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Diagnosing IAQ Problems 45

Yes

Diagnosing IAQ Problems

The goal of the diagnostic buildinginvestigation is to identify and solve theindoor air quality complaint in a way thatprevents it from recurring and that does notcreate other problems. This sectiondescribes a method for discovering thecause of the complaint and presents a“toolbox” of diagnostic activities to assistyou in collecting information.

Just as a carpenter uses only the toolsthat are needed for any given job, an IAQinvestigator should use only the investiga-tive techniques that are needed. Manyindoor air quality complaints can beresolved without using all of the diagnostictools described in this chapter. Forexample, it may be easy to identify thesource of cooking odors that are annoyingnearby office workers and solve theproblem by controlling pressure relation-ships (e.g., installing exhaust fans) in thefood preparation area. Similarly, mostmechanical or carpentry problems prob-ably require only a few of the many toolsyou have available and are easily accom-plished with in-house expertise.

The use of in-house personnel buildsskills that will be helpful in minimizingand resolving future problems. On theother hand, some jobs may be best handledby contractors who have specializedknowledge and experience. In the sameway, diagnosing some indoor air qualityproblems may require equipment and skillsthat are complex and unfamiliar. Yourknowledge of your organization andbuilding operations will help in selectingthe right tools and deciding whether in-house personnel or outside professionalsshould be used in responding to thespecific IAQ problem.

6Start (reason for concern)

Initial walkthrough■ preparation■ visual inspection■ talk with occupants and staff

Collect additionalinformation about■ building occupants■ the HVAC system■ pollutant pathways■ pollutant sources

(sample contaminants if needed)

Develop one or more hypothesesto explain the problem. Test bymanipulating building conditionsor exposure, or by performingappropriate tests.

Is theproblemsolved ?

Make necessarychanges so thatthe problem willnot recur.

Finish

Yes

No

No

No Yes

▼

▼

▼

▼

▼

▼

▼

▼

Note: Outside assistance may be needed at anypoint in the investigation, depending upon thecomplexity of the problem, the skills available in-house, time pressures, or other factors.

FIGURE 6-1:Conducting an IAQ Investigation

Do you havean explanation

for the complaint ?

Do resultssupport yourhypothesis ?

Attempta controlstrategy

▼

Follow-upvalidation

46 Section 6

OVERVIEW: CONDUCTING ANIAQ INVESTIGATION

An IAQ investigation begins with one ormore reasons for concern, such as occu-pant complaints. Some complaints can beresolved very simply (e.g., by asking a fewcommon sense questions of occupants andfacility staff during the walkthrough). Atthe other extreme, some problems couldrequire detailed testing by an experiencedIAQ professional. In this section “theinvestigator” refers to in-house staffresponsible for conducting the IAQinvestigation.

The flowchart on page 45 shows thatthe IAQ investigation is a cycle of infor-mation-gathering, hypothesis formation,and hypothesis testing. The goal of theinvestigation is to understand the IAQproblem well enough so that you can solveit. Many IAQ problems have more thanone cause and may respond to (or require)several corrective actions.

Initial Walkthrough

An initial walkthrough of the problem areaprovides information about all four of thebasic factors influencing indoor air quality(occupants, HVAC system, pollutantpathways, and contaminant sources). Theinitial walkthrough may provide enoughinformation to resolve the problem. At theleast, it will direct further investigation.For example, if the complaint concerns anodor from an easily-identified source (e.g.,cooking odors from a kitchen), you maywant to study pollutant pathways as a nextstep, rather than interviewing occupantsabout their patterns of discomfort.

Developing and TestingHypotheses

As you develop an understanding of howthe building functions, where pollutantsources are located, and how pollutantsmove within the building, you may thinkof many “hypotheses,” potential explana-

tions of the IAQ complaint. Buildingoccupants and operating staff are often agood source of ideas about the causes ofthe problem. For example, they candescribe changes in the building that mayhave occurred shortly before the IAQproblem was noticed (e.g., relocatedpartitions, new furniture or equipment).

Hypothesis development is a processof identifying and narrowing downpossibilities by comparing them with yourobservations. Whenever a hypothesissuggests itself, it is reasonable to pauseand consider it. Is the hypothesisconsistent with the facts collected so far?

You may be able to test your hypothesisby modifying the HVAC system orattempting to control the potential sourceor pollutant pathway to see whether youcan relieve the symptoms or other condi-tions in the building. If your hypothesissuccessfully predicts the results of yourmanipulations, then you may be ready totake corrective action. Sometimes it isdifficult or impossible to manipulate thefactors you think are causing the IAQproblem; in that case, you may be able totest the hypothesis by trying to predict howbuilding conditions will change over time(e.g., in response to extreme outdoortemperatures).

Collecting AdditionalInformation

If your hypothesis does not seem to be agood predictor of what is happening in thebuilding, you probably need to collectmore information about the occupants,HVAC system, pollutant pathways, orcontaminant sources. Under somecircumstances, detailed or sophisticatedmeasurements of pollutant concentrationsor ventilation quantities may be required.Outside assistance may be needed ifrepeated efforts fail to produce a successfulhypothesis or if the information requiredcalls for instruments and procedures thatare not available in-house.

The IAQ investigationis often a repetitivecycle of information-gathering, hypothesisformation, andhypothesis testing.


Results of the Investigation

Analysis of the information collectedduring your IAQ investigation couldproduce any of the following results:

The apparent cause(s) of the complaint(s)are identified.

Remedial action and follow-up evaluationwill confirm whether the hypothesis iscorrect.

Other IAQ problems are identified thatare not related to the original complaints.

These problems (e.g., HVAC malfunc-tions, strong pollutant sources) should becorrected when appropriate.

A better understanding of potential IAQproblems is needed in order to develop aplan for corrective action.

It may be necessary to collect moredetailed information and/or to expand thescope of the investigation to includebuilding areas that were previouslyoverlooked. Outside assistance may beneeded.

The cause of the original complaintcannot be identified.

A thorough investigation has found nodeficiencies in HVAC design or operationor in the control of pollutant sources, andthere have been no further complaints. Inthe absence of new complaints, the originalcomplaint may have been due to a single,unrepeated event or to causes not directlyrelated to IAQ.

Using Outside Assistance

Some indoor air quality problems may bedifficult or impossible for in-houseinvestigators to resolve. Special skills orinstruments may be needed. Other factorscan also be important, such as the benefitof having an impartial outside opinion orthe need to reduce potential liability from a

serious IAQ problem. You are best able tomake the judgment of when to bring in anoutside consultant. See Section 8 for adiscussion of hiring professional assistanceto solve an IAQ problem.

INITIAL WALKTHROUGH

An investigation may require one or manyvisits to the complaint area. The amountof preparatory work needed before theinitial walkthrough varies with the natureand scope of the complaint and theexpertise of the investigator, among otherfactors. For example, an in-house investi-gator who is already familiar with thelayout and mechanical system in thebuilding may begin responding to acomplaint about discomfort by goingdirectly to the complaint area to check thethermostat setting and see whether air isflowing from the supply outlets.

If the investigator is not familiar withthe building or is responding to complaintsthat suggest a serious health problem, morepreparation may be needed before theinitial walkthrough. The activities listedbelow can be directed at a localized“problem area” or extended to include theentire building:

Collect easily-available information aboutthe history of the building and of thecomplaints.

Identify known HVAC zones and com-plaint areas.

Begin to identify potential sources andpollutants (e.g., special use areas near thecomplaint location). Having a copy ofmechanical and floor plans can be helpfulat this stage, especially if they arereasonably up-to-date.

Notify the building occupants of theupcoming investigation.

Tell them what it means and what toexpect.

48 Section 6

to describe the operating schedule ofequipment. Obvious problems (e.g.,blocked diffusers, malfunctioning airhandlers) can be corrected to see if thecomplaints disappear. The walkthroughcan solve many routine IAQ problems andwill suggest directions for a more complexinvestigation, should one be necessary.

Some investigators avoid taking anymeasurements during the initial walk-through so that they are not distracted from“getting the big picture.” Others find thatusing smoke sticks, digital thermometers,and direct reading CO

2 meters or detector

tubes to take occasional measurementshelps them develop a feel for the building.

It may help to keep the followingquestions in mind during the initialwalkthrough:

Are there obvious pollutant sources? Dothey appear to be adequately controlled?

■ Are pollutant indicators present, such asodors, excessive dust, or staining?

■ Are there sanitation problems (e.g.,debris near outdoor air intake, visiblemold growth, major water damage) thatcould be introducing air contaminants?

■ Are there any conditions or activitiesoccurring in or near the building thatcould be related in timing, location andhealth effects to the complaints?

Are there any deficiencies in the HVACsystem that serves the complaint area?

■ Does equipment serving the area (e.g.,thermostats, diffusers, fans, dampers,filters) appear to be operating, clean, andin good condition?

■ Do operating procedures exist, and doesthe staff follow them?

■ Do records indicate that the system wascommissioned (set, tested, and balanced)after construction?

■ Do records indicate that system compo-nents are regularly inspected, calibrated,and adjusted?

This improvised catch basinis intended to collect waterseeping into the building frombelow grade. Although thecatch basin “solves” the prob-lem of uncontrolled waterleakage, it also provides anindoor location that couldsupport the growth ofmicrobiologicals and createIAQ problems.

Identify key individuals needed for accessand information.

A person familiar with the HVAC systemsin the building should be available to assistthe investigator at any time during theonsite phase. Individuals who havecomplained or who are in charge ofpotential sources (e.g., housekeeping, non-HVAC equipment) should be aware thattheir information is important and shouldbe contacted for appointments or telephoneinterviews if they will not be availableduring the onsite visit.

The initial walkthrough provides anopportunity to question complainants aboutthe nature and timing of their symptomsand to briefly examine the immediate areaof the complaint. The investigatorattempts to identify pollutant sources andtypes and observes the condition andlayout of the HVAC system serving thecomplaint area. Facility staff can be asked


Are there pathways and pressure differ-ences which could be moving contami-nants into the complaint area from theoutdoors or from other parts of thebuilding?

COLLECTING ADDITIONALINFORMATION

Additional information will be needed ifthe initial walkthrough does not identifythe cause of the problem. The followingpages present techniques for collectinginformation about the occupant com-plaints, HVAC system, pollutant pathways,and pollutant sources and using thatinformation to develop a hypothesis thatcould explain the problem. Common sensewill suggest the appropriate sequence ofsteps during this part of the investigation.For example, if the complaint is limited toa single room, it makes sense to evaluatepollutant pathways into that room beforeattempting to inventory sources in loca-tions outside of, but connected to, thecomplaint area. On the other hand, if thecomplaint involves a recognizable odor(e.g., exhaust fumes), it may be morepractical to begin by locating the potentialsource(s) of the odor before trying toidentify pollutant pathways.

Forms and checklists such as thesamples provided in this document (modi-fied if needed) can help investigators torecord information in an organized way.Small copies of basic floor plans, such asfire evacuation plans, are convenient fornoting locations of observations.

Any instruments that will be usedshould be inspected to make sure they arein working order and calibrated. IAQinvestigations generally include the use of,at a minimum: heatless chemical smokedevices and instruments for measuringtemperature and humidity.

Carbon dioxide measuring devices(detector tubes with a hand pump or adirect reading meter) are helpful for mostinvestigations. Other instruments may beneeded as the investigation progresses.See Appendix A for additional guidance oncommon IAQ measurements.

Tools for Collecting Information

The following pages present strategies,tools, and forms for the investigator to useduring an in-depth investigation. TheIncident Log shown below (and in Tab V)can be used to track the course of an inves-tigation from the receipt of the originalcomplaint.

Sample FormIncident Log

Investigation Record(check the forms that were used)

DateFileNumber

Outcome /Comments

Log Entry By(initials)

Problem Location

SEECOMPLETEFORMPAGE 183

50 Section 6

buildings. They are intended to present aproblem-solving approach that can helpfacility staff to understand and resolvemany common indoor air quality prob-lems. If you decide to hire outsideprofessionals to resolve your IAQ com-plaint, this discussion of strategies andtools should help you to understand andoversee their investigative work.

COLLECTING INFORMATIONABOUT OCCUPANTCOMPLAINTS

Occupant data falls into two categories:complaints of discomfort or other symp-toms (e.g., teary eyes, chills) and percep-tions of building conditions (e.g., odors,draftiness). Investigators can gathervaluable information about potentialindoor air problems from listening tooccupants, and use that information for:

■ defining the complaint area within thebuilding

■ suggesting directions for further investi-gation, either by identifying other eventsthat seem to happen at the same time asthe incidents of symptoms or discomfort,or by identifying possible causes for thetypes of symptoms or discomfort that areoccurring

■ indicating potential measures to reduceor eliminate the problem

Review Existing Records ofComplaints

If there is a record of occupant complaints,a review of that record can help to definethe location of the IAQ problem andidentify people who should be interviewedas part of the investigation. Informationabout the history of complaints could alsostimulate theories about potential causes ofthe problem.

Interview Occupants

The most obvious way to collect informa-tion from building occupants is to talk to

COLLECTING OCCUPANT INFORMATION

Strategies Tools

Review existinginformation aboutcomplaints

Collect additionalinformation fromoccupants

■ Existing Records■ IAQ Complaint Form■ Incident Log

■ Occupant Interview■ Occupant Diary

An initial walkthrough mayuncover problems such asthis unsanitary condition inthe HVAC system. Birddroppings have collected inan air supply plenum near anoutdoor air intake that wasnot protected by a birdscreen.

The discussion that follows has beendivided into categories of occupant data,HVAC system data, pollutant pathwaydata, and source data. However, thesuggestions for collecting and usinginformation reflect the interdependence ofthese factors. For example, the operationof the air distribution system affectspollutant pathways, and the air distributionsystem can also be a source of pollutants.

Indoor air quality-related complaintsmay develop from a variety of causes.Neither the discussion of strategies forcollecting information nor the suggestionsfor interpreting data can present the fullrange of possible situations encountered in


Sample FormOccupant Interview


them in person. If it is not possible tointerview everyone who has complainedabout building conditions, the investigatorshould attempt to interview a group ofindividuals that reflect the concerns of theaffected areas.

The investigation may also includeoccupant interviews with building occu-pants who do not have complaints. Thenconditions in the complaint area can becompared to conditions in similar buildinglocations where there are no complaints.

A sample Occupant Interview form isshown here (there is another copy inTab V). It can also be presented in awritten form in order to get informationfrom more people than can be interviewed.The following key points will helpinterviews to be productive:

■ Read the discussion of evaluatingoccupant data before you conductinterviews, to be certain that youunderstand what sort of information isneeded.

■ Make a copy of the interview form foreach person you speak with, and use theform to record the answers to yourquestions.

■ Choose a location in which the personyou are interviewing feels comfortable tospeak freely.

■ Explain that the interview is intended tohelp discover and correct the cause of thecomplaints. Encourage the person youare interviewing to join in this coopera-tive problem-solving effort.

■ Give the person you are interviewingenough time to think about your ques-tions.

■ If complainants are reluctant to answerquestions about health symptoms,respect their desire for privacy. Planningfor how to maintain this privacy iswarranted, and in some cases may bemandated.

■ Feel free to expand the interview byadding questions that help to improveyour understanding or explore their

hypotheses (or your own) about whatmay be causing the problem. Always beopen to answers that may not fit yourhypotheses.

■ You may sometimes need to clarify aquestion by giving examples of the sortof information you are interested in. Tryto provide more than one example so thatyou don’t seem to be telling the personthe answer you want. Be particularlycautious about mentioning specifichealth effects.

The Occupant Interview includesmany basic points that are found inquestionnaires used by professional IAQinvestigators. It is important to note,however, that this form is not called a“questionnaire.” Formal questionnairesmay be useful for quantitative epidemiol-ogy, IAQ research, complex IAQ investi-gations, or when litigation is a possibility.In these cases, questionnaires must becarefully designed and executed by peoplewith an understanding of representativesampling and expertise in public health,industrial hygiene, or medicine. Use ofquestionnaires for such purposes is beyondthe scope or expertise of most in-houseinvestigations; if such questionnaire data is

SYMPTOM PATTERNSWhat kind of symptoms or discomfort are you experiencing?

Are you aware of other people with similar symptoms or concerns?Yes____ No____

If so, what are their names and locations?

Do you have any health conditions that may make you particularlysusceptible to environmental problems?

TIMING PATTERNSWhen did your symptoms start?

52 Section 6

On the form below, please record each occasion when you experiencea symptom of ill-health or discomfort that you think may be related toan environmental condition in the building.

Sample FormOccupant Diary

Time/Date Location Symptom Severity/Duration Comments

Sample FormLog of Activities and System Operations

On the form below, please record your observations of HVAC systemoperation, maintenance activities, and any other information that youthink may be helpful in identifying the cause of IAQ complaints in thisbuilding. Please report any other observations (e.g., weather, otherassociated events) that you think may be important as well.

Equipment and activities of particular interest:Air Handler(s):Exhaust Fan(s):Other Equipment or Activities:

Date/Time Day of Week Equipment Item/Activity Comments

SEECOMPLETEFORMSPAGES 187AND 189

needed, building owners and managersshould use professionals.

Ask Occupants and FacilityStaff to Keep More DetailedRecords

Many events occur simultaneously in andaround a complex building, and it can bevery difficult to judge which of thoseevents might be related to the IAQcomplaints. In trying to resolve stubbornproblems, professional investigatorssometimes ask occupants and facility staffto keep day-by-day records. Occupants areasked to record the date and time ofsymptoms, where they are when thesymptoms appear, and any other informa-tion that might be useful. Such informa-tion could include observations about theseverity and duration of symptoms andcomments on weather conditions, events,and activities that are happening at thesame time. Facility staff are asked torecord the date and time of events such asmaintenance work, equipment cycles, ordeliveries. If symptoms seem to occur atparticular times of day, staff can focustheir attentions on recording events thatoccur before and during those periods.Such records are likely to produce moreaccurate and detailed information than canbe obtained by relying on memory. (Usethe Occupant Diary and the Log ofActivities and System Operations shownhere and included in Tab V.)


Exhaust fumes are drawn intothis building’s outdoor airintake when trucks are idlingat the nearby loading dock.Tools such as the OccupantDiary and Log of Activitiesand System Operation canhelp to identify intermittentpollutant sources such as thisone.

USING THE OCCUPANT DATA

The pattern of complaints within thebuilding helps to define the complaint area.The timing of symptoms and the types ofsymptoms reported may provide cluesabout the cause of the problem.

Strategies for Using Occupant Data

■ Define the complaint area■ Look for timing patterns■ Look for symptom patterns

54 Section 6

SPATIAL PATTERNS

Widespread, no apparent spatialpattern

Localized (e.g., affecting indi-vidual rooms, zones, orair handling systems)

Individual(s)

SUGGESTIONS

■ Check ventilation and tem-perature control for entirebuilding.

■ Check outdoor air quality.■ Review sources that are spread

throughout building (e.g.,cleaning materials).

■ Consider explanation other thanair contaminants.

■ Check ventilation and tempera-ture control within the complaintarea.

■ Review pollutant sourcesaffecting the complaint area.

■ Check local HVAC systemcomponents that may be actingas sources or distributors ofpollutants.

■ Check for drafts, radiant heat(gain or loss), and otherlocalized temperature control orventilation problems near theaffected individual(s).

■ Review local pollutant source(s)near the affected individual(s).

■ Consider that common back-ground sources may affect onlysusceptible individuals.

■ Consider the possibility thatindividual complaints may havedifferent causes that are notnecessarily related to thebuilding (particularly if symp-toms differ among the individu-als).

Define the Complaint Area

Use the spatial pattern (locations) ofcomplaints to define the complaint area.Building locations where symptoms ordiscomfort occur define the rooms or zonesthat should be given particular attentionduring the initial investigation. However,the complaint area may need to be revisedas the investigation progresses. Pollutantpathways can cause occupant complaintsin parts of the building that are farremoved from the source of the problems.


Look for Timing Patterns

Look for patterns in the timing of com-plaints. The timing of symptoms andcomplaints can indicate potential causesfor the complaints and provide directionsfor further investigation. Review the datafor cyclic patterns of symptoms (e.g.,worst during periods of minimum ventila-tion or when specific sources are mostactive) that may be related to HVACsystem operation or to other activities inand around the building.

TIMING PATTERNS SUGGESTIONS

■ Review HVAC operating cycles.Emissions from buildingmaterials, or from the HVACsystem itself, may build upduring unoccupied periods.

■ Consider that ventilation maynot be adequate to handleroutine activities or equipmentoperation within the building.

■ Look for daily, weekly, orseasonal cycles or weather-related patterns, and checklinkage to other events in andaround the building.

■ Consider spills, otherunrepeated events as sources.

■ Ask staff and occupants todescribe recent changes orevents (e.g., remodeling,renovation, redecorating, HVACsystem adjustments, leaks, orspills).

■ Consider that the problem islikely to be building-related,though not necessarily due to airquality. Other stressors (e.g.,lighting, noise) may be involved.

■ Consider that the problem maynot be building-related.

Symptoms begin and/orare worst at the start ofthe occupied period

Symptoms worsen overcourse of occupied period

Intermittent symptoms

Single event of symptoms

Recent onset of symptoms

Symptoms relieved on leaving thebuilding, either immediately,overnight, or (in some cases) afterextended periods away from thebuilding

Symptoms never relieved,even after extended absence frombuilding (e.g., vacations)

56 Section 6

which toxicology has found specificeffects. Therefore, it may be more usefulto look for patterns of symptoms thanfor specific pollutant and health effectrelationships.

Investigators who are not medicallytrained cannot make a diagnosis and shouldnot attempt to interpret medical records.Also, confidentiality of medical informa-tion is protected by law in some jurisdic-tions and is a prudent practice everywhere.

Look for Symptom Patterns

Look for patterns in the types of symptomsor discomfort. IAQ investigations oftenfail to prove that any particular pollutantor group of pollutants are the cause of theproblem. Such causal relationships areextremely difficult to establish. There islittle information available about the healtheffects of many chemicals. Typical indoorlevels are much lower than the levels at

The following chart lists somecommon symptom groupsthat can be related to indoorair quality, along with possiblesources or causes of thosesymptoms. Buildingmanagers are cautioned thatthis is only a partial listing.

SYMPTOM PATTERNS

THERMAL DISCOMFORT

COMMON SYMPTOM GROUPSHeadache, lethargy, nausea,drowsiness, dizziness

Congestion; swelling, itching orirritation of eyes, nose, orthroat; dry throat; may beaccompanied by non-specificsymptoms (e.g. headache,fatigue, nausea)

Cough; shortness of breath;fever, chills and/or fatigue afterreturn to the building

Diagnosed infection

Suspected cluster of rare orserious health problems suchas cancer, miscarriages

OTHER STRESSORSDiscomfort and/or healthcomplaints that cannot bereadily ascribed to air contami-nants or thermal conditions

SUGGESTIONS

■ Check HVAC condition and operation.■ Measure indoor and outdoor temperature and humidity (see Figure 6-2 on

page 57). See if extreme conditions exceed design capacity of HVAC equip-ment.

■ Check for drafts and stagnant areas.■ Check for excessive radiant heat gain or loss.

If onset was acute, arrange for medical evaluation, as the problem may be carbonmonoxide poisoning.■ Check combustion sources for uncontrolled emissions or spillage. Check

outdoor air intakes for nearby sources of combustion fumes.■ Consider evacuation/medical evaluation if problem isn’t corrected quickly.■ Consider other pollutant sources.■ Check overall ventilation; see if areas of poor ventilation coincide with com-

plaints.

May be allergic, if only small number affected; more likely to be irritationalresponse if large number are affected.■ Urge medical attention for allergies.■ Check for dust or gross microbial contamination due to sanitation problems,

water damage, contaminated ventilation system.■ Check outdoor allergen levels (e.g., pollen counts).■ Check closely for sources of irritating chemicals such as formaldehyde or those

found in some solvents.

May be hypersensitivity pneumonitis or humidifier fever. A medical evaluationcan help identify possible causes.■ Check for gross microbial contamination due to sanitation problems, water

damage, or contaminated HVAC system.

May be Legionnaire’s disease or histoplasmosis, related to bacteria or fungi foundin the environment.■ Contact your local or State Health Department for guidance.

■ Contact your local or State Health Department for guidance.

■ Check for problems with environmental, ergonomic, and job-relatedpsychosocial stressors.


FIGURE 6-2: Acceptable Ranges of Temperature and RelativeHumidity During Summer and Winter 1

Relative Humidity Winter Temperature Summer Temperature

30% 68.5°F - 76.0°F 74.0°F - 80.0°F

40% 68.5°F - 75.5°F 73.5°F - 79.5°F

50%2 68.5°F - 74.5°F 73.0°F - 79.0°F

60% 68.0°F - 74.0°F 72.5°F - 78.0°F

1 Applies for persons clothed in typical summer and winter clothing, at light,mainly sedentary activity.2 See left for discussion of relative humidities.

SOURCE: Adapted from ASHRAE Standard 55-1981, Thermal EnvironmentalConditions for Human Occupancy

Figure 6-2 shows the range of tempera-tures and relative humidities that fallwithin the comfort zone for most individu-als dressed in “typical” clothing andinvolved in light, mostly sedentaryactivity. Recent research suggests thatindoor air quality is judged to be worse astemperatures rise above 76°F, regardless ofthe actual air quality.

There is considerable debate amongresearchers, IAQ professionals, and healthprofessionals concerning recommendedlevels of relative humidity. In general, therange of humidity levels recommended bydifferent organizations seems to be 30% to60%. Relative humidities below thislevel may produce discomfort fromdryness. On the other hand, maintainingrelative humidities at the lowest possiblelevel helps to restrict the growth of moldand mildew. The concerns (comfort forthe most part) associated with dry air mustbe balanced against the risks (enhancedmicrobiological growth) associated withhumidification. If temperatures aremaintained at the lower end of the comfortrange (68 - 70°F) during heating periods,relative humidity in most climates will notfall much below 30% (also within thecomfort range) in occupied buildings.

COLLECTING INFORMATIONABOUT THE HVAC SYSTEM

IAQ complaints often arise because thequantity or distribution of outdoor air isinadequate to serve the ventilation needs ofbuilding occupants. Problems may also betraced to air distribution systems that areintroducing outdoor contaminants ortransporting pollutants within the building.

The investigation should begin with thecomponents of the HVAC system(s) thatserve the complaint area and surroundingrooms, but may need to expand if connec-tions to other areas are discovered. Yourgoal is to understand the design andoperation of the HVAC system well

enough to answer the following questions:

■ Are the components that serve theimmediate complaint area functioningproperly?

■ Is the HVAC system adequate for thecurrent use of the building?

■ Are there ventilation (or thermal com-fort) deficiencies?

■ Should the definition of the complaintarea be expanded based upon the HVAClayout and operating characteristics?

An evaluation of the HVAC systemmay include limited measurements oftemperature, humidity, air flow, and CO

2,

as well as smoke tube observations.Complex investigations may require moreextensive or sophisticated measurements ofthe same variables (e.g., repeated CO

2

measurements taken at the same locationunder different operating conditions,continuous temperature and relativehumidity measurements recorded with adata logger). A detailed engineering studymay be needed if the investigation discov-ers problems such as the following:

■ airflows are low■ HVAC controls are not working or are

working according to inappropriatestrategies

■ building operators do not understand (orare unfamiliar with) the HVAC system

WHAT DO YOUKNOW SO FAR?

■ Use the HypothesisForm on page 223 tomake brief notes afterreviewing the occupantdata.

■ Decide whether youhave a hypothesis thatmight explain thecomplaints. If so, test it.(See page 78 for adiscussion ofhypothesis testing.

■ Decide what else youneed to know.Consider whetherin-house expertise issufficient or outsideassistance is needed(See Section 8 forguidance on hiringoutside assistance.)

58 Section 6

COLLECTING HVAC SYSTEM INFORMATION

Strategies

Review existing documen-tation on HVAC design,installation, and operation

Talk to facilities staff

Inspect system layout,condition, and operation

Use additional instrumentsas appropriate

Tools

Collect:■ design documents, testing and

balancing reports■ operating instructions, control

manufacturer’s installation data

Ask facilities staff to record their observa-tions of equipment cycles, weatherconditions, and other events usingLog of Activities and System Operations

Use:■ Zone/Room Record■ HVAC Checklist - Short Form and/or■ HVAC Checklist - Long Form■ thermometer and sling psychrometer

(or electronic equivalent) to measuretemperature and humidity

■ micromanometer (or equivalent) tomeasure pressure differentials● 0-2" and 0-10" water gauge (w.g.)

to measure at fans and intakes

● 0-.25" w.g. with pitot tube to checkairflow in ducts

■ chemical smoke for observing airflowpatterns

■ a device to assess airflow fromdiffusers● rough quantitative: anemometer;

velometer● accurate quantitative: flow hood

■ carbon dioxide measurement devices● detector tubes with a hand pump● direct reading meter

Instruments often used by professionalIAQ consultants include:■ a hygrothermograph to log temperature

and humidity■ tracer gas and measurement equip-

ment■ a device to measure airborne particu-

lates■ measurement devices for carbon

monoxide and other contaminantsof interest

Review Documentation onHVAC Design, Installation, andOperation

A review of existing documentation (e.g.,plans, specifications, testing and balancingreports) should provide information aboutthe original design and later modifications,particularly:■ the type of HVAC system (e.g., constant

volume, VAV)■ locations and capacities of HVAC

equipment serving the complaint area■ the planned use of each building area■ supply, return, and exhaust air quantities■ location of the outdoor air intake and of

the supply, return, and exhaust registers,diffusers, and grilles that serve thecomplaint area

The most useful way to record thisinformation is to make a floor plan of thecomplaint area and surrounding rooms.You may be able to copy an existing floorplan from architectural or mechanicaldrawings, fire evacuation plans, or someother source.

If there is no documentation on themechanical system design, much more on-site inspection will be required to under-stand the HVAC system. The HVACsystem may have been installed ormodified without being commissioned,so that it may never have performedaccording to design. In such cases, goodobservations of airflow and pressuredifferentials are essential. In addition, loadanalyses may be required.

Talk to Facility Staff

Facility staff can provide important currentinformation about equipment operating andmaintenance schedules and breakdowns orother incidents. There may be inspectionreports or other written records availablefor review. Staff members who arefamiliar with building systems in generaland with the specific features of the


building under investigation can be veryhelpful in identifying conditions that mayexplain the indoor air quality complaints.Some facility operators have extensivepreventive maintenance programs. On theother hand, discussion could reveal thatfacility staff are not operating the buildingaccording to its design, because:■ they do not understand the design logic

of the HVAC system■ they have been asked to run the HVAC

system at the lowest possible energy cost■ they do not have the manpower to

operate the building properly■ the HVAC system has not been modified

to accommodate changes in the use ofspace or increases in the occupantpopulation

Staff may have noticed occupantactivities that are indicators of inadequateventilation or poorly-controlled tempera-tures, such as:■ desktop fans, heaters, or humidifiers■ supply diffusers blocked off with tape or

cardboard■ popped-up ceiling tiles■ interference with thermostat settings

IAQ complaints are often intermittent.Discussions with staff may reveal patternsthat relate the timing of complaints to thecycles of equipment operation or to otherevents in the building such as painting,installation of new carpeting, or pestcontrol. These patterns are not necessarilyobvious. Keeping a day-to-day record mayhelp to clarify subtle relationships betweenoccupant symptoms, equipment operation,and activities in and around the building.(See Occupant Diary and Log of Activi-ties and System Operations on page 52and in Tab V.) Staff members may havetheories about the cause ofthe problem.

Inspect System Layout,Condition, and Operation

If the building is new or if there is a pre-ventive maintenance program with recent

Above: An investigation of this buildingrevealed no problems with the HVAC sys-tem, although the amount of outdoor air wasvery low. In a more thorough inspection ofthe HVAC system, investigators found thatthe wiring to this outdoor air damper motorhad never been connected. No outdoor airwas entering the building through the intakecontrolled by this damper. Below: Theseinvestigators are examining a perimeter fan-coil unit. Self-contained heating or coolingunits such as this one are often overlookedduring routine maintenance. There may bemany such units in a single building, some-times in remote or inaccessible locations.

60 Section 6

test and balance reports, it is possible (butnot necessarily likely) that the HVACsystem is functioning according to itsoriginal design. Otherwise it is probablethat one or more features of building usageor system operation have changed in waysthat could affect indoor air quality.

Elements of the on-site investigationcan include (but are not limited to) thefollowing:

Check temperature and/or humidity to seewhether the complaint area is in the com-fort range.

Take more than one measurement to ac-count for variability over time and fromplace to place. Compare to Figure 6-2 onpage 57 (see also Appendix B ).

■ Check thermostat operation.■ Check whether the supply air tempera-

ture corresponds to the design criteria.■ Use a hygrothermograph (if available) to

log temperature and humidity changes inthe complaint area.

The design specifications forthis building called for a mini-mum 20% setting on theoutdoor air damper control.Facility staff lowered theminimum outdoor air settingto 10% in order to save en-ergy and reduce operatingcosts. As a result, the build-ing was underventilatedwhenever outdoor tempera-tures were either very hot orvery cold.

Check for indicators of inadequateventilation.

■ Check supply diffusers to see if air ismoving (using chemical smoke). If it isnot, confirm that the fan system is operat-ing, and then look for closed dampers,clogged filters, or signs of leaks.

■ Compare design air quantities (if avail-able) to building codes for the currentoccupancy or ventilation guidelines (e.g.,ASHRAE 62-1989, see Appendix B). Ifthe HVAC system, performing as de-signed, would not provide enough venti-lation air for current needs, then there isgood reason to believe that actual ventila-tion rates are inadequate.

■ Measure carbon dioxide (CO2) in the

complaint area to see whether it indicatesventilation problems. (See Appendix Afor a discussion of techniques for measur-ing and interpreting CO

2 concentrations.)

■ Measure air quantities supplied to andexhausted from the complaint area, in-cluding calculation of outdoor air quanti-ties (see Appendix A for further guid-ance). Be aware of damper settings andequipment cycles when you are measur-ing (e.g., are you evaluating minimumoutdoor air, “normal” conditions, ormaximum airflow?). Note that evalua-tion of variable air volume (VAV) sys-tems requires considerable expertise.Compare the measured air quantities toyour mechanical system design specifica-tions and applicable building codes. Alsocompare ventilation rates to ASHRAE62-1989. Some of the ventilation recom-mendations of ASHRAE 62-1989 arereproduced in Appendix B.

Check that equipment serving the com-plaint area (e.g., grilles, diffusers, fans) isoperating properly.

■ Confirm the accuracy of reported operat-ing schedules and controls sequences; forexample, power outages may have dis-rupted time clocks, fans reported as“always running” may have been acci-dentally switched off, and controls can bein need of calibration.


The dark streaks at theoutlet of this supply diffusercould indicate a filtration prob-lem. Poorly maintained or im-properly sized filterscan allow dirt to be distrib-utedthrough the building.

■ Check to see that equipment is properlyinstalled. For example, look for shippingscrews that were never removed or fansthat were reversed during installation, sothat they move air in the wrong direc-tion.

Compare the current system to theoriginal design.

■ Check to see that all equipment calledfor in the original design was actuallyinstalled.

■ See whether original equipment mayhave been replaced by a different model(i.e., a model with less capacity or differ-ent operating characteristics).

See whether the layout of air supplies,returns, and exhausts promotes efficientair distribution to all occupants and iso-lates or dilutes contaminants.

(See Appendix A for guidance on usingchemical smoke to study airflow and mix-ing patterns and CO

2 to help determine the

adequacy of ventilation.)

■ If supplies and returns are close together,heatless chemical smoke can be used tocheck for short-circuiting (supply air thatdoes not mix properly with air in thebreathing zone, but moves directly to thereturn grille). CO

2 can also be used to

evaluate air mixing.■ Use heatless chemical smoke to observe

airflow patterns within the complaintarea and between the complaint area andsurrounding spaces, including outdoors.Compare airflow directions under vari-ous operating conditions.

■ If the system layout includes ceilingplenums, look above the ceiling for inter-ruptions such as walls or full-heightpartitions.

Consider whether the HVAC system itselfmay be a source of contaminants.

■ Check for deterioration or unsanitaryconditions (e.g., corrosion, water damageor standing water, mold growth or exces-

sive dust in ductwork, debris or damagedbuilding materials in ceiling plenums).

■ If the mechanical room serves as a mix-ing plenum (i.e., return and outdoor airare drawn through the room into the airhandler), check very carefully for poten-tial contaminants such as stored solventsand deteriorated insulation.

Use the forms provided in this documentto inspect the HVAC system.

■ Use the Zone/Room Record to describethe ventilation system serving the com-plaint area and surrounding rooms orzones. The Zone/Room Record isreproduced on page 62 and in Tab V.

■ Use the HVAC Checklist (short and/orlong form) to evaluate the condition ofHVAC system components that affect airdistribution and IAQ in the complaintarea. A portion of the HVAC Checklist-Short Form is reproduced on page 62.The HVAC Checklist - Long Form isuseful for more detailed examination ofthe system. Complete copies of bothforms can be found in Tab V.

62 Section 6

This form is to be used differently depending on whether the goal is to prevent or diagnose IAQ problems.During development of a profile, this form should be used to record more general information about the entirebuilding; during an investigation, the form should be used to record more detailed information about thecomplaint area and areas surrounding the complaint area or connected to it by pathways.

Zone/Room RecordSample Form

PROFILE AND DIAGNOSIS INFORMATION DIAGNOSIS INFORMATION ONLY

Building Area(Zone/Room)

Use** Source ofOutdoor Air*

MechanicalExhaust?

(Write “No”or estimatecfm airflow)

Comments Peak Number ofOccupants or

Sq. Ft. Floor Area*

Total AirSupplied(in cfm)**

Outdoor AirSupplied

per Person orper 150 sq.Ft. Area****

Sample Form

HVAC Checklist — Short Form

Sections 2, 4 and 6 and Appendix B discuss the relationships between theHVAC system and indoor air quality.

MECHANICAL ROOM

■ Clean and dry? Stored refuse or chemicals?

■ Describe items in need of attention

MAJOR MECHANICAL EQUIPMENT

■ Preventive maintenance (PM) plan in use?

Control System

Type

System operation

USING THE HVAC SYSTEMDATA

As you review the HVAC data, considerwhether the system is adequate to servethe use of the building and whether thetiming, location, and impact of apparentdeficiencies appear related to the IAQcomplaint. Deficiencies in HVACdesign, operation, or maintenance mayexist without producing the complaintunder investigation; some defects maynot cause any apparent IAQ problems.

Strategies for Using the HVACSystem Data

■ Compare the original design to thecurrent system.

■ Compare the original uses of space tocurrent uses.

■ Consider the condition of the HVACsystem.



HEALTH AND SAFETY CONSIDERATIONS FORIAQ INVESTIGATORS

Normal safety precautions observed during routine operation of the building must befollowed closely during IAQ inspections. When the IAQ investigator is not familiar withthe mechanical equipment in that particular facility, an operator or engineer should bepresent at all times in equipment areas. Potential safety hazards include:

■ electrocution■ injury from contacting fans, belts, dampers or slamming doors■ burns from steam or hot water lines■ falls in ventilation shafts or from ladders or roofs

Investigators evaluating building IAQ generally do not encounter situations in whichspecific personal protection measures (e.g., protective garments and respirators) arerequired. However, safety shoes and eyeglasses are generally recommended forworking around mechanical equipment. When severe contamination is present (e.g.,microbiological, chemical, or asbestos), IAQ investigators may need additionalprotection in the vicinity of certain building areas or equipment. Such decisions aresite specific and should be made in consultation with an experienced industrialhygienist. General considerations include the following:

Microbiological: Care must be taken when serious building related illness (e.g.,Legionnaire’s disease) is under investigation or when extensive microbiological growthhas occurred. Investigators with allergy problems should be especially cautious. Thearray of potential contaminants makes it difficult to know what sort of personal protec-tion will be effective. At a minimum, investigators should minimize their exposure to airin the interior of ducts or other HVAC equipment unless respiratory protection is used.If there is reason to suspect biological contamination (e.g., visible mold growth), expertadvice should be obtained about the kind of respiratory protection to use and how touse it. Possible protective measures against severe microbiological contaminationinclude disposable coveralls and properly fitted respirators.

Chemical: Where severe chemical contamination is suspected, specific precautionsmust be followed if OSHA action levels are approached. Such instances rarely occurin IAQ investigations. One possible exception might be a pesticide spill in a confinedspace. In this case, an appropriate respirator and disposable coveralls may beneeded.

Asbestos: An IAQ investigation often includes inspection above accessible ceilings,inside shafts, and around mechanical equipment. Where material suspected ofcontaining asbestos is not only present, but also has deposited loose debris, theinvestigator should take appropriate precautions. This might include disposablecoveralls and a properly fitted respirator.

Note: The requirements for proper fit, physical condition of the wearer, and other considerationsinvolved in selection of the proper respirator must be evaluated by an occupational safety andhealth specialist. There is a NIOSH Respirator Decision Logic for proper respirator selection, andOSHA has regulations for an appropriate respirator protection program.

When the IAQ investi-gator is not familiarwith the mechanicalequipment in thatparticular facility, anoperator or engineershould be present atall times in equip-ment areas.

64 Section 6

Compare the Original Design tothe Current HVAC System

Consider the original HVAC design andcompare it to the current equipment,layout, and controls. A variety of HVACsystem designs have been used in publicand commercial buildings. The type ofsystem used in your building affects thecontrol of ventilation air quantities anddistribution, as well as thermal comfort.See Appendix B for a discussion of HVACsystem types.

SUGGESTIONS

■ Revise definition of complaint area (ifneeded) to add spaces linked to theoriginal complaint area by ductwork orcontrols.

■ Check to see that thermostatsare properly located and functionproperly.

■ Note equipment changes thatcould be affecting the system’sperformance (e.g., removal or additionof equipment, replacement by a differ-ent model).

■ Review operating procedures for oc-cupied and unoccupied periods.

■ Compare timing of occupied/unoccupied periods to equipmentcycles and occupant complaints.Confirm that time clocks are readingthe actual time. See ASHRAE 62-1989 for suggested lead times to allowproper flushing before occupants ar-rive. In some cases (e.g., warm, hu-mid climates), fans may need to oper-ate during unoccupied periods to pre-vent mold growth or other problems.

ALL SYSTEMS

Ventilation andtemperaturecontrol zones

Changes inequipment

Operatingcycles


Use HVAC Data to EvaluateMitigation Measures

As you use the HVAC data to evaluatepotential mitigation measures, review thesuggestions made in both the box on thefacing page for all HVAC systems and inthe box on this page for the type of HVACsystem in your building.

SUGGESTIONS

■ Identify the source(s) of ventilation air(e.g., operable windows, doorspropped open).

■ Check whether the location of openwindows, doors, or other openingspromotes the introduction of odors orcontaminants.

■ Check whether outdoor air intakes areobstructed. Does their location pro-mote the introduction of odors or con-taminants?

■ Note design airflows in the complaintarea (outdoor air, supply, return, andexhaust) and surrounding spaces;compare to ASHRAE 62-1989 and to actual measuredairflows.

■ Note design airflows in the complaintarea (outdoor air, supply, return, andexhaust) and surrounding spaces;compare to applicable building codes,ASHRAE 62-1989, and to actual mea-sured airflows.

■ Check whether outdoor air intakes areobstructed. Does their location pro-mote the introduction of odors or con-taminants? Check for unsanitary con-ditions.

■ Check outdoor air damper controls.

In addition to all suggestions made forconstant volume systems:

■ Confirm whether the system design al-lows regulation of outdoor air quanti-ties. Do VAV boxes have stops to en-sure that minimum amounts of out-door air are delivered at all times dur-ing occupied periods? Are the systemcontrols providing a constant ventila-tion rate per person regardless of totalsystem airflows?

■ Observe changes (if any) in airflowpatterns within and around the com-plaint area as the VAV systemthrottles from maximum tominimum flow.

SYSTEM TYPES

No mechanicalventilation orexhaust only

Room units(e.g., unitventilators)

Constantvolume

Variableair volume(VAV)

66 Section 6

Compare the Original Uses ofSpace to Current Uses

Compare the original uses of the complaintarea and surrounding rooms to currentuses of those areas. Indoor air qualityproblems often arise when the usage ofrooms changes without correspondingadjustments to the HVAC system. Forexample, if ventilation appears to be aproblem despite a properly-functioningHVAC system, the existing system maybe inadequate to meet current needs.

SUGGESTIONS

■ Compare temperature and humidity tocomfort zone in ASHRAE 55-1981guidelines.

■ Compare minimum outdoor airquantities to the original design,applicable building codes, andASHRAE 62-1989 guidelines.

For example introduction of a morephysically active group of occupants canchange thermal comfort requirements.


■ Compare minimum outdoor airquantities to the original design,applicable building codes, andASHRAE 62-1989 guidelines.

■ Check for low-level contaminantsources.


■ Consider the need for local exhaust atpoint sources of contaminants.

Example: Modifications that convert oradd such special uses as smokinglounges, print shops, or kitchen facilitiesmay also require changes in theoperation of the HVAC system.

■ Check pressure relationships betweenspecial use areas and surroundingspaces.

■ Consider the need for local exhaust atpoint sources of contaminants.

■ Check that thermostats are properlylocated. Compare temperature andhumidity to comfort zone in ASHRAE55-1981 guidelines.

■ Check layout of supplies, returns, andexhausts.

■ Check to make sure that partitions donot block proper air circulation.

ROOM USE CHANGES

Increased occupantdensity

Change in type of occu-pant population

Additional non-HVACequipment

Conversion to or additionof special uses

Rearrangement of workstations (e.g., relocation ofpartitions)


SYSTEM CONDITIONS

Unsanitary conditions■ Moisture or standing water■ Debris■ Dust and/or mold growth

HVAC malfunctions■ Equipment breakdown■ Obstructed diffusers or grilles■ Air distribution or mixing problems:

(e.g., equipment isout of balance, requirescalibration, or needs other adjust-ment)

■ Air bypasses filters (due toloose filter tracks, incorrect filtersize, or filter overloaded with dirt)

■ Air distribution system leaks (e.g.,leaky ductwork; unin-tendedopenings in pressurized ceilings orin return air plenums)

HVAC functions properly.However, there is evidence ofunderventilation.

SUGGESTIONS

■ Correct sanitary problems andadopt necessary measures toprevent recurrence of problems.

■ Evaluate whether the HVACdefect could have caused theIAQ complaint.

■ Correct the malfunction(s), andsee whether complaints areresolved.

■ Review maintenance programand revise as needed to preventfuture problems.

■ Consider what adjustmentscould be made to increase thesupply of outdoor air (ordecrease the ventilationdemand) in the complaint area.

Consider the Condition of theHVAC System

Consider whether the HVAC system isreasonably clean and functioning properly.Review the results of the onsite inspection.If you identified sanitary or operatingproblems in the HVAC system serving thecomplaint area, you may want to correctthose problems and see whether thecomplaints are resolved before continuingwith the investigation.


■ Use the HypothesisForm on page 223 tomake brief notes.

■ Decide whether youhave a hypothesisthat might explain thecomplaints. If so, testit. (See page 78 for adiscussion of hypoth-esis testing.)

■ Decide what else youneed to know.Consider whether in-house expertise issufficient or outsideassistance is needed(See Section 8 forguidance on hiringoutside assistance.)

68 Section 6

COLLECTING INFORMATIONABOUT POLLUTANT PATHWAYSAND DRIVING FORCES

Unless the IAQ problem is caused by anobvious contaminant located in thecomplainant’s immediate workspace, youwill need to understand the patterns ofairflow into and within the complaint area.Correction of IAQ problems often involvescontrolling pollutant movement throughsealing of pollutant pathways or manipula-tion of the pressure relationships.

If the complaints being investigated arelimited to a few areas of the building, pollut-ant pathways can be evaluated so that thecomplaint area is properly defined beforeconducting the source inventory. If com-plaints are spread throughout the building,

evaluation of pathways could be a verytime-consuming process, and it may bemore practical to look for major contami-nant sources before trying to discover howthe contaminants move within the building.

Identify Pollutant Pathways

Architectural and mechanical pathwaysallow pollutants to enter the complaint areafrom surrounding spaces, including theoutdoors. An examination of architecturaland mechanical plans can help in develop-ing a list of connections to surroundingareas. These include:

■ doors■ operable windows■ stairways■ elevator shafts■ utility chases■ ductwork and plenums■ areas served by common HVAC controls

(e.g., shared thermostats)

Onsite inspection is needed to confirmthe existence of these connections and toidentify other openings (e.g., accidentalopenings such as cracks and holes). Firecodes usually require that chases and hid-den openings be firestopped. Check for theexistence and condition of firestops inchases, especially those that connect bothvertically and horizontally.

Chemical smoke is beingused to detect the directionand amount of airflow throughthis closed doorway. Abuilding investigator mustknow how the ventilation inthe building is designed tooperate in order to decidewhether the observed flow ofsmoke is appropriate.

Identify pollutantpathways

Observe directionof air movement

■ Architectural and mechanicaldrawings

■ Pollutant Pathway Form for Investigations■ Sketch plan of complaint area

■ Testing and balancing reports■ Chemical smoke tests■ Micromanometer or equivalent

COLLECTING PATHWAY INFORMATION

Strategies Tools


Building Name File Number

Address:

Completed By (name):

The Pollutant Pathway Form forInvestigations shown to the right can beused along with a sketch plan of thecomplaint area (similar to the example onpage 70) to record pathways and directionsof pollutant movement. A blank copy ofthe form is included in Tab V.

Observe Air MovementDirection

The airflow quantities shown in mechani-cal plans or in testing and balancingreports can be used to determine thedirection of air movement intended by thedesigner. Onsite examination is necessaryto determine the actual direction of airflowat each available pathway.

Chemical smoke tubes can be used todetermine airflow directions between thecomplaint area and surrounding spaces(including the outdoors), and to reveal aircirculation patterns within the complaintarea. A micromanometer (or equivalent)can measure the magnitude of pressuredifferences between these areas. Thesketch plan and the Pollutant PathwayForm for Investigations can be used torecord the results.

It may be necessary to make observa-tions under different conditions, as airflowdirection can change depending uponweather conditions, windspeed anddirection, equipment operation within thebuilding, traffic through doors, and otherfactors (e.g., as VAV systems throttleback). Switching air handlers or exhaustfans on and off, opening and closing doors,and simulating the range of operatingconditions in other ways can help to showthe different ways that airborne contami-nants move within the building. Dusttracking patterns around door frames canreveal the dominant direction of air andpollutant movement.

Some investigators study air movementby releasing a small amount of peppermintoil at the opening to a suspected pathwayand asking an assistant to sniff for the

Pollutant Pathway for Investigations FormSample Form

“toothpaste” smell. If this technique isused, it is important that the assistant havean acute sense of smell. If the building isin use during the investigation, occupantsmay also notice the odor and could find itdistracting. Some investigators prefer touse methods that release an odor duringunoccupied periods. Investigators shouldnote two common causes of false negativeresults (falsely concluding that no pathwayexists):

■ The nose quickly becomes tolerant ofstrong odors, so that the assistant mayneed to take a long rest (breathing freshair) between tests.

■ If there is substantial airflow through thepathway, the peppermint oil odor couldbe diluted so that it is imperceptible.

Tracer gases such as sulfur hexafluo-ride (SF

6) can provide qualitative and

quantitative information on pollutant path-ways and ventilation rates. Use of tracergases to obtain quantitative results re-quires considerable technical expertise. Ifit appears that a sophisticated study ofpathways (or ventilation rates) is required,you need to use trained investigators.

Rooms or ZonesConnected to the

Complaint Area byPathways

Pressure Relative toComplaint AreaUse

Comments(e.g., potential

polluntantsources)+/- date/time



Evaluate Airflow Patterns

Evaluate airflow patterns into andwithin the complaint area. Because ofthe complexity and variability of air-flow patterns, investigators cannot beexpected to understand how air moveswithin the building under all potentialoperating conditions. However, dataon pathways and driving forces canhelp to locate potential pollutantsources and to understand how con-taminants are transported to buildingoccupants.

SUGGESTIONS

■ Look for temporal patternslinking changes in airflowdirection to incidents ofcomplaints.

■ Look for spatial patternslinking potential sources tothe locations of complaints.


■ Use the HypothesisForm on page 223 tomake brief notes afterreviewing the pollutantpathway data.

■ Decide whether youhave a hypothesis thatmight explain thecomplaints. If so, test it.(See page 78 for adiscussion of hypothesistesting.)

■ Decide what else youneed to know. Considerwhether in-houseexpertise is sufficient oroutside assistance isneeded. (See Section 8for guidance on hiringoutside assistance.)

AIRFLOW PATTERNS

■ Onsite observations

Confirm or Revise Bound-aries of the Complaint Area

The discovery of unexpected pollutantpathways can show a need to studyareas of the building that may bedistant from the original complaintarea.

COMPLAINT AREA

■ Complaint area connectedby architectural features toother areas

■ Complaint area connectedby mechanical system toother areas

■ Unintentional pathways(e.g., cracks, holes)

SUGGESTIONS

■ Check whether pressure relationshipsbetween complaint area and sur-rounding locations follows intent ofventilation design.

■ Check whether air from otherlocations flows into the complaintarea under some conditions. If so,consider expanding the investigationto inventory pollutant sources (andperhaps collect HVAC or occupantdata) in those locations.

72 Section 6

COLLECTING SOURCE INFORMATION

Strategies Tools

Conduct onsiteinspection

Talk with buildingoccupants, facilitiesstaff, and contractors

■ Pollutant and Source Inventory■ Chemical Inventory

■ Pollutant and Source Inventory■ Chemical Inventory

COLLECTING INFORMATIONON POLLUTANT SOURCESThroughout the investigation, the buildinginvestigator will try to identify pollutantsources that may be causing the occupantcomplaints. Any public or commercialbuilding is likely to contain a number ofsources that produce odors, contaminants,or both. The investigator’s task is toidentify the source(s) that may be respon-sible for the complaint(s).

The area included in the pollutant sourceinventory should be defined by the invest-igator’s understanding of the building’sarchitectural and mechanical layout andpollutant pathways. Common sense willhelp to differentiate unusual sources (e.g.,spills, strong odors from new furnishingsor equipment) from those that are normallyfound within or near the building.

Remember that very few sources ofindoor air contaminants are both continu-ous and constant in volume over time.Pollutant concentrations often vary instrength over time, and may not be evidentat the time of the site visit. Some sourcesare subtle and might only be noticed by atrained investigator. As the investigationprogresses, the inventory of pollutantsources may need to be revised by expand-ing the definition of the complaint area orexamining specific locations more closely(e.g., under various operating conditions).

Onsite InspectionDepending upon the nature of the com-plaint, the investigator may find some ofthe following activities to be useful. Thislist is not intended to be complete.

Inventory outdoor sources■ Examine the area around the outdoor air

intake for unsanitary conditions, standingwater, or nearby pollutant sources suchas exhaust vents or motor vehicles.

■ Observe patterns of traffic, constructionactivity, and other potential sources inthe neighborhood of the building.

Sample FormPollutant and Source Inventory Form

Using the list of potential source categories below, record anyindications of contamination or suspected pollutants that may requirefurther investigation or treatment.

Source Category Checked Needs Attention Location Comments

SOURCES OUTSIDE THE BUILDING

Contaminated Ambient Air

Pollen, dust

Industrialcontaminants

General vehicularcontaminants

The inventory should include chemicals stored or used in the buildingfor cleaning, maintenance, operations, and pest control.

Date Chemical/ Use Storage MSDS Brand Name Location(s) on File?

Sample FormChemical Inventory



■ Inquire about outdoor ambient airproblems in the area. (This informationmay be available from your local HealthDepartment.)

■ Observe soil gas entry points.

Inventory equipment sources■ Review non-HVAC equipment, particu-

larly large office equipment such asengineering drawing reproductionmachines and wet-process copiers.Learn about usage patterns and identifyitems that are not equipped with localexhaust.

■ Review biocides, water treatment usedon HVAC equipment.

Review building components andfurnishings■ Check drain traps to make sure they are

not dry.■ Identify areas of excessive dust and/or

deteriorated furnishings.■ Identify areas of soil or water damage.■ Identify locations of new furnishings.

Inventory other potential sources■ Identify special use areas such as

smoking lounges, laboratories, printshops.

■ Identify areas where remodeling, repair,or redecorating activities are in progressor recently completed. Check proce-dures being used to isolate demolitiondust, paint fumes, and other contami-nants related to the process.

■ Inventory cleaning materials used in thebuilding.

(See Section 4 for another discussion ofproblem indicators and common problemsthat may become obvious during awalkthrough of the building.)

The Pollutant and Source Inventorycan be used to record your observations.The Chemical Inventory form is intendedto serve as a record of materials such assolvents, biocides, pesticides, and cleaningcompounds that may require special care instorage and handling. Material SafetyData Sheets (MSDSs) should be collected

on these materials whenever possible.(See Section 4 for further discussion ofMSDSs.) Portions of both forms areshown on the poopsite page; the completeform is included in Tab V.

Talk With Building Occupantsand Facility StaffBuilding occupants and facility staff canprovide valuable information about thelocation and timing of activities thatproduce odors or contaminants (e.g.,smoking, cooking, housekeeping, mainte-nance). They may also suggest explana-tions for the IAQ problem that can help inthe development of hypotheses. Facilitystaff and outside contractors (e.g., personsinvolved in housekeeping, pest control, orremodeling) should be interviewed orasked to provide a current list of materials,procedures, and schedules used forcleaning and pest control.

It may be useful to discuss the followingitems with building occupants:

Inventory activities■ Review smoking policy (and actual

practice; cleaning staff may know wheresmoking occurs in violation of policy,especially in private offices).

■ Identify areas of overcrowding.■ Review products used for housekeeping,

maintenance, and pest control and theschedules of their use.

■ Inquire about housekeeping schedulesand procedures.

■ Identify supply storage areas and checkfor well-sealed containers and properventilation.

Discuss incidents that could be sources■ Inquire about prior and neighboring uses

of land (e.g., landfills, underground fueltanks).

■ Inquire about events such as spills, fires,or leaks.

■ If such events have occurred, learn whatremedial actions were taken to clean upafter the incidents and to prevent theirrecurrence.

74 Section 6

PATTERNS

Location(s)of sources

Timingof emissions

SUGGESTIONS

■ Compare locations of sources to locations ofcomplaint(s).

■ Identify pathways linking potential sources to thecomplaint area.

■ Revise definition of complaint area if necessary.

■ Note whether the sources emit on a continuousor intermittent basis.

■ Compare the timing of emissions to the timingof complaints.

■ Identify occasions when the source is likely to bestrongest.

■ Determine whether pathways between thesource(s) and the complaint location couldaccount for the occasions of complaints.


■ Use the HypothesisForm on page 223 tomake brief notes afterreviewing the pollutantsource data.

■ Decide whether youhave a hypothesisthat might explain thecomplaints. If so, testit. (See page 78 for adiscussion of hypoth-esis testing.)

■ Decide what else youneed to know.Consider whether in-house expertise issufficient or outsideassistance is needed.(See Section 8 forguidance on hiringoutside assistance.)

USING POLLUTANT SOURCEDATA

If a strong pollutant source is identified inthe immediate vicinity of the complaint, asimple test (e.g., sealing, covering, orremoving the source) can sometimes revealwhether or not it is the cause of the IAQproblem. If a number of potential sourceshave been found in and around thecomplaint area, other data (e.g., the patternof symptoms, the HVAC system designand operation, and pollutant pathways)may be needed in order to determine whichsource(s), if any, may be related to thecomplaint.

Strategies for Using SourceInformation

■ Identify patterns linking emissions tocomplaints

■ Evaluate unrelated sources

Identify Patterns LinkingEmissions to Complaints

Look for patterns linking emissions frompotential sources to the IAQ complaints.

Evaluate Unrelated Sources

Evaluate sources that appear unrelated tothe complaints. It is not unusual to

identify potential contaminant sources thatare unrelated to the present IAQ complaint(i.e., either the location of the source, thetiming of emissions, or both fit poorly withthe pattern of complaints). These shouldbe prioritized for remedial work accordingto their potential for causing healthproblems or complaints in the future.

A detailed study of pollutants andsources may involve an engineeringevaluation of equipment that is releasingIAQ contaminants, diagnostic sampling toassess sources in operation, or othermeasurements. These may require skills orinstruments that are not available in-house.

SAMPLING AIR FORCONTAMINANTS ANDINDICATORS

Although air sampling might seem to bethe logical response to an air qualityproblem, such an approach may not berequired to solve the problem and can evenbe misleading. Air sampling should not beundertaken until some or all of the otherinvestigative activities mentioned previ-ously have been used to collect consider-able information. Before beginning to takeair samples, investigators should develop asampling strategy that is based on acomprehensive understanding of how thebuilding operates, the nature of thecomplaints, and a plan for interpreting theresults.

It may be desirable to take certainroutine air quality measurements during aninvestigation to obtain a “snapshot” ofcurrent conditions. These tests should belimited to those that are indicative of verycommon IAQ concerns such as tempera-ture, relative humidity, air movement, orcarbon dioxide (CO

2). Unusual readings

may or may not indicate a problem, andshould always be interpreted in perspec-tive, based upon site-specific conditions.

Measurement of specific chemical orbiological contaminants can be veryexpensive. Before expending time and


money to obtain measurements of indoorair pollutants, you must decide:

■ how the results will be used(e.g., comparison to standards orguidelines, comparison to levels incomplaint-free areas)

■ what substances(s) should be measured■ where to take samples■ when to take samples■ what sampling and analysis method to

use so that the results provide usefulinformation

It is often worthwhile for building staffto develop skills in making temperature,humidity, airflow, and CO

2 measurements

and assessing patterns of air movement(e.g., using chemical smoke). Appendix Aprovides a brief introduction to ventilationand thermal measurement strategies and tomethods of sampling for specific aircontaminants.

How Will the Results Be Used?

Although air sampling will generatenumbers, it will not necessarily helpresolve the IAQ problem. Many IAQcomplaints are resolved without samplingor with inconclusive sampling results.

The design of an air sampling strategyshould fit the intended use of the measure-ments. Potential uses of indoor airmeasurements include:

1. Comparing different areas of the buildingor comparing indoor to outdoor condi-tions in order to:

Confirm that a control approach hasthe desired effect of reducing pollutantconcentrations or improving ventilation

Establish baseline conditions so thatthey can be compared to concentrationsat other times or locations, such as

■ concentrations in outdoor air■ concentrations in areas where no

symptoms are reported

■ expected “background” range fortypical buildings without perceivedIAQ problems

Test a hypothesis about the source of theproblem, such as■ checking emissions from a piece of

equipment

2. Testing for “indicator” compoundsassociated with particular types ofbuilding conditions:

Peak carbon dioxide (CO2 ) concentra-tions over 1000 ppm (parts per million)are an indicator of underventilation

Carbon monoxide (CO) over severalppm indicates inappropriate presenceof combustion by-products (which mayalso account for high CO2 readings)

3. Comparing measured concentrationsto guidelines or standards

Occupational exposure standards andguidelines, such as■ OSHA PELs (Occupational Safety and

Health Administration’s PermissibleExposure Limits)

■ NIOSH RELs (National Institute forOccupational Safety and Health’sRecommended Exposure Limits)

■ ACGIH TLVs (American Conferenceof Governmental Industrial Hygienists’Threshold Limit Values)

Occupants in this one-storyoffice building were complain-ing of intermittent gasolineodors. Exhausts from under-ground gasoline storage tankvent pipes (visible in thelower right portion of thisphotograph) were beingdrawn into the office buildingthrough outdoor air intakes onthis roof. The gasoline stor-age tanks belonged to anadjacent service station.

76 Section 6

Public health guidelines for specificpollutants■ EPA National Ambient Air Quality

Standards■ World Health Organization Air Quality

Guidelines■ Canadian Exposure Guidelines for

Residential Air Quality

There are no widely accepted proceduresto define whether IAQ test results are ac-ceptable. Extreme caution must be used incomparing contaminant concentrations toexisting occupational standards and guide-lines. Although a contaminant concentra-tion above those guidelines is a clear prob-lem indicator, occupants may still experi-ence health and comfort problems at con-centrations well within those guidelines. Itis extremely rare for occupational stan-dards to be exceeded — or even ap-proached — in public and commercialbuildings, including those experiencingindoor air quality problems.

Where specific exposure problems aresuspected, more detailed diagnostic testingmay be needed to locate or understandmajor sources, confirm the exposure, andto develop appropriate remedial actions.For example, the control of microbial orpesticide contamination may involve sur-face or bulk sampling. (Surface samplinginvolves wiping a measured surface areaand analyzing the swab to see what organ-isms are present, while bulk samplinginvolves analyzing a sample of suspectmaterial.) Specialized skills, experience,and equipment may be needed to obtain,analyze, and interpret such measurements.

What Substance(s) Should BeMeasured?

Measurement of “indicator” compoundssuch as CO

2 or CO can be a cost-effective

strategy. Such measurements can help theinvestigator understand the nature of theproblem and define the complaint area.

Air sampling for specific pollutantsworks best as an investigative tool when itis combined with other types of informa-tion-gathering. It is prudent to begin aprogram of chemical sampling only ifsymptoms or observations strongly suggestthat a specific pollutant or a specific sourcemay be the cause of the complaint and ifsampling results are important in determin-ing an appropriate corrective action.

Where Should Air Samples BeTaken?

The identified problem area is an obvioussite for air sampling. Measurements takenoutdoors and in a control location (e.g., acomplaint-free area of the building) arehelpful in interpreting results from thecomplaint area.

The conditions experienced by buildingoccupants are best simulated by samplingair from the “breathing zone” away fromthe influence of any particular individual.However, if an individual sits at a desk allday (except for brief periods), samplersplaced on the desk when the individual iselsewhere can provide a good estimate ofthat person’s exposure.

There are several ways to locate sam-pling sites for an IAQ investigation. Oneapproach first divides the building intohomogeneous areas based on key factorsidentified in the building inspection andinterviews. Examples of how a buildingmight be divided include:

■ control zones (e.g., individual rooms)■ types of HVAC zones (e.g., interior vs.

perimeter)■ complaint vs. non-complaint areas■ relationship to major sources

(e.g., spaces directly, indirectly, or notimpacted by smoking areas)

■ complaint types

Test sites can then be selected to repre-sent complaints, controls, and potentialsources with a reasonable number ofsamples.

It is prudent to begina program of chemi-cal sampling only ifsymptoms or obser-vations stronglysuggest that a spe-cific pollutant or aspecific source maybe the cause of thecomplaint and ifsampling results areimportant in deter-mining an appropriatecorrective action.


When Should Indoor AirSamples Be Taken?

Samples may be designed to obtain “worst-case” conditions, such as measurementsduring periods of maximum equipmentemissions, minimum ventilation, or distur-bance of contaminated surfaces. Worst-case sample results can be very helpful incharacterizing maximum concentrations towhich occupants are exposed and identify-ing sources for corrective measures.

It is also helpful to obtain samples duringaverage or typical conditions as a basis ofcomparison. It may, however, be difficultto know what conditions are typical. Re-search shows that exposure to some pollut-ants may vary dramatically as buildingconditions change. Devices that allowcontinuous measurements of key variablescan be helpful.

Symptoms or odors that only occur occa-sionally will not generally be seen duringthe IAQ investigation. Air samples shouldnot be taken if an incident is not occurring,unless the purpose of the sample is to es-tablish a baseline for future comparisons.

One approach to intermittent IAQ prob-lems is for the IAQ investigator to askappropriate building staff or other occu-pants to document changes over time usingday-to-day records such as the OccupantDiary and Log of Activities and SystemOperation. When an odor episode doesoccur, the building engineer could inspectthe air handler and intake area while an-other staff member documents the status ofseveral potential sources.

Another strategy is to manipulatebuilding conditions to create worst-caseconditions during the building investiga-tion (e.g., arrange for the trash truck to idleat the loading dock or close outdoor airdampers to minimum settings). Chemicalsmoke and tracer gases can be used toassess where emissions may travel undervarious building conditions. (Suchstrategies should be carried out in waysthat minimize occupant exposure.)

Investigators shouldbear in mind thatcomplaints producedby these stressorsare sometimes mis-takenly blamed oncontaminated air. Tocomplicate matters,such stressors alsocan produce a height-ened sensitivity topoor indoor air qual-ity.

What Sampling and AnalysisMethod Should Be Used?

Take care to select appropriate measure-ment techniques and to provide interpreta-tions so that the results provide usefulinformation. Appendix A providesguidance on measurement techniques thatare commonly used in IAQ investigations.

COMPLAINTS DUE TOCONDITIONS OTHER THANPOOR AIR QUALITY

Complaints that initially seem to be linkedto thermal discomfort, underventilation, orindoor air pollutants may actually becaused or complicated by factors such as:

■ environmental stressors (e.g., lighting,noise, vibration)

■ ergonomic stressors■ job-related psychosocial (human rela-

tions) stressors

The following briefly discusses each ofthese three kinds of stressors. Investiga-tors should bear in mind that complaintsproduced by these stressors are sometimesmistakenly blamed on contaminated air.To complicate matters, such stressors alsocan produce a heightened sensitivity topoor indoor air quality. Thus, even whenspecific stressors are obvious, the investi-gator should not assume that they are theonly reason for the complaints.

Lighting

Stresses from inadequate or poorlydesigned lighting (e.g., glare, flicker, poorillumination of work surfaces) can producesymptoms such as eyestrain and head-aches. Lack of natural sunlight can also bea source of stress. These complaints aresometimes mistakenly interpreted as signsof poor indoor air quality. Lightingproblems may be evident in large areas orlocalized in particular workspaces.

78 Section 6

The glare from the windowswas causing a variety ofoccupant complaints in thisbuilding and was disruptingthe workers’ ability to use thevideo display terminals.Complaints such asheadaches are sometimesincorrectly blamed on poorindoor air quality.

Noise

Noisy surroundings can reduce the abilityto concentrate and produce stress-relatedsymptoms such as headaches. Noise canalso contribute to job dissatisfaction,particularly if the problem is caused byovercrowding or other factors likely toproduce a sense of substandard workconditions.

The ear gets used to sounds quickly, so itis possible for a complainant to be unawareof a constant or regular sound. Investiga-tors should recognize that noise can be asource of stress, even if it is not reported asa problem and is within current industrialexposure criteria (which are designedprimarily to prevent hearing loss).

Vibration

Low-frequency vibration is another sourceof stress that may go unreported bybuilding occupants or become confusedwith pollutant problems. Vibration can becaused by nearby machinery or movementof the building as a whole; motion sicknesshas been reported in some high risebuildings that sway in the wind.

Ergonomic Stressors

Fatigue, circulatory problems, and otherphysical problems can be produced byfurniture that is mismatched to the task,such as chairs that are the wrong height forcomputer terminals. If IAQ investigatorsinquire about whether new furniture hasrecently been installed in the problem area(to determine if the furniture could becontributing to increased contaminantlevels), they should also ask aboutwhether the occupant finds the furniturecomfortable.

Job-related PsychosocialStressors

It is well documented that various job-related psychosocial conditions canproduce symptoms in workers. Excessiveworkload and work pressure are easilyrecognized job stressors. Lack of clarityabout what is expected of the worker (roleambiguity) and the presence of conflictingexpectations (role conflict) are alsocommonly encountered stressors inmodern organizations. Poor interpersonalrelations, management styles that allowlittle participation in decision-making, andfactors related to career development arealso thought to be potentially stressful.

FORMING AND TESTINGHYPOTHESES

As the building investigation progresses,you should be developing one or morehypotheses that could explain the occupantcomplaints. The investigation can then beshaped to collect information that willeither support or refute your hypotheses.

The Hypothesis Form on the oppositepage is designed to pull together theseparate pieces of information that havebeen collected by summarizing the resultsof the investigation. More pages can beadded if desired, but the form is designedfor brief notes that can be scanned easily.As you review the information, write down


any explanation(s) for the IAQ problem thatmake sense, and think about how thepieces of the puzzle fit together whenbuilding conditions are compared tooccupant complaints.

Is all (or most) of your informationconsistent with your hypothesis? If not, isthere a reasonable explanation for theinconsistencies? A different hypothesismight provide a better fit with yourinformation.

You may find that there are several IAQproblems (e.g., underventilation in onezone, a strong contaminant source inanother room). If you have discoveredpotential IAQ problems that do not appearrelated to the original complaint, they canbe prioritized and corrected as time andfunding permit.

Think of ways to test your hypotheses.You may want to change ventilation rates,change the pressure relationship betweenspaces, cover or remove suspected sources,seal pathways, or temporarily relocateaffected individuals. If your manipulationscan reduce occupant complaints, you havefound a reasonable hypothesis. Sometimesit is not possible (or not practical) tomanipulate important factors. You can alsotest your hypothesis by seeing how accu-rately you can predict changes in buildingconditions (e.g., as outdoor temperaturechanges).

If you are having difficulty developinghypotheses, review the information youhave collected and the suggestions abouthow to use that information. For sugges-tions on using occupant complaint data, seepages 53-57; on using HVAC systeminformation, see pages 62-67; on usingpollutant pathway information, see pages70-71; on using pollutant/source inventorydata, see page 74; on using air samplinginformation, see pages 75-76.

The changes that are made duringhypothesis testing may offer a practicalsolution to the IAQ problem, or may beonly temporary measures. The mitigationchapter presents a variety of approachesthat have been used in correcting someselected categories of IAQ problems anddiscusses how to evaluate those strategies.


Sample FormHypothesis Form

Complaint Area (may be revised as the investigation progresses):

_______________________________________________________________

_______________________________________________________________

Complaints (e.g., summarize patterns of timing, location, peopleaffected):

_______________________________________________________________

_______________________________________________________________

HVAC: Does the ventilation system appear to provide adequate air,efficiently distributed to meet occupant needs in the complaint area? Ifnot, what problems do you see?

_______________________________________________________________

_______________________________________________________________

Pathways: What pathways and driving forces connect the complaintarea to locations of potential sources?

_______________________________________________________________

_______________________________________________________________

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