iaq sampling

IAQ Sampling

• Document a condition or state of the space– Adequate ventilation– Comfort

• Identify source of contamination– Leakage– Products

Choice of Instrument

• Depends on the task

• For most applications a simpler, less expensive instrument will suffice

Types of IAQ Instruments

• Direct Reading or Continuous Instruments– Passive– Active

• Integrated samples– Passive– Active– Grab sample

Direct reading instruments

• Give an instantaneous value.

• Requires zeroing and calibration or point checking

• Instrument chosen depends on sensitivity required

• Optical instruments require periodic maintenance from manufacturer

• Interferences

Active vs Passive

• Active instruments use a pump to draw air over the sensor.

• Passive instruments rely on diffusion of air across the sensor.

• Active instruments have lower sensitivity than passive instruments.

Uses of Instruments

• Instruments are used either to measure a contaminant or a property or condition of the space.

• Particulates, gases, noise, mold, moisture are examples of contaminants

• Temperature, RH, Light, Air Flow are examples of properties

Isopropyl CPC: Particle size range of 0.01 to >1.0 µm Concentration range of 0 to 100,000 particles/cm3

5x105 particles/cm3

Water-based CPC Detects particles down to 6 nm

Isopropyl P-Trak -Concentration Range 0 to 5 × 105 particles/cm3, Particle Size Range 0.02 to 1 micrometer

UFP Particle Counters

UFP Particle Counters

• Identify emissions from combustion or indoor chemistry

• Identify changes in ventilation conditions

• Monitor clean rooms

• Identify leakage from processes

Alcohol CPC W-CPC

Indoor Chemistry• VOC’s- vapor organic

compounds at typical indoor temperatures

• Ex: formaldehyde, benzene, chloroform, pinene

• Some react with OZONE

Case Study - Air Cabin

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Ozone ppb

Altitude (ft)

Ultrafine p/cc

Measures PM1, PM2.5, Respirable, PM10 and TPM simultaneously with no need for

size-selective inlet conditioners.

Aerosol Concentration Range 0.001 to 20 mg/m3 (calibrated to respirablefraction of ISO 12103-1, A1 test dust)Particle Size Range 0.1 to 10 micrometer (μm)Minimum Resolution 0.001 mg/m3

Nephelometers/Particle Counters

0.001 to 400 mg/m3DustTrak

personalDataRam

SidePak

Met One GT-526 Six Channel Particle Counter0.3, 0.5, 0.7, 1.0, 2.0 and 5.0 um

Nephelometers

• Measures light scattering

• Converts to mass using an algorithm

• Subject to interferences primarily from size distribution of aerosol and humidity

• Newer models have place for in-line filter to correct against gravimetric value

• More expensive monitors have a filtered are flow sheen to protect optics

Range0 to 9,999 ft/min (0 to 50 m/s)

0 to 200°F (-18 to 93°C)

Multiputpose IAQ tools• Measure several

parameters with one device.

• CO2 –Passive - NDIR• CO-Passive-

electrochemical• Temp• RH• Pressure• Air flow• etc

NDIR Sensors

• NDIR sensors are spectroscopic sensors to detect CO2 in a gaseous environment by its characteristic absorption.

• The key components are an infrared source, a light tube, an interference (wavelength) filter, and an infrared detector.

• The gas is pumped or diffuses into the light tube, and the electronics measures the absorption of the characteristic wavelength of light.

• NDIR sensors are most common sensor for measuring carbon dioxide.

• Sensitivities range from 20-50 PPM.

Electrochemical sensors

• Electrochemical sensors operate by reacting with the gas of interest and producing an electrical signal proportional to the gas concentration.

• Sensing electrode (or working electrode), and a counter electrode separated by athin layer of electrolyte.

• Gas passes through a small capillary-type opening and then diffuses through a hydrophobic barrier in to the electrolyte.

• The gas reacts at the surface of the sensing electrode involving either an oxidation or reduction mechanism. These reactions are catalyzed by the electrode materials specifically developed for the gas of interest.

MIRAN SapphIRe Portable Ambient Analyzer utilizes infrared spectroscopy to accurately measure many gases with a single instrument.Wavelength coverage permits outstanding single and multi-gas monitoring as well as unknown compound identification.

Portable trace gas detection

Other Monitors

PID

Ventilation Assessment

• Air Flow

• Ventilation Rate

• HVAC Balance

• Air currents

• Temperature

• RH

• Air Tightness

Flow Range30 to 2,000 cfm (15 to 1,000 l/s, 50 to 3,500 m3/hr)Accuracy±5% reading and ±5 cfm (±2.4 l/s, ±8.5 m3/hr)Operating Temperature32 to 140°F (0 to 60°C) 0.25 to 30 m/s (50 to 6,000 ft/min)

Diameter 4 in. (100mm)

Balometer

Air Flow HoodVane anemometer

Measures differential and static pressure from -15 to +15 in. H2O (-3735 to +3735 Pa)

Micro manometer and pitot tube

Blower Door

Used to measure infiltration in homes. Estimates effective leakage area

Heat Stress/Radiant Temperature Monitors

IR Thermometer

Surface Temperature

IR Thermometer

• A lens to collect the energy emitted by the target• A detector to convert the energy to an electrical

signal• An emissivity adjustment to match the IRT

calibration to the emitting characteristics of the object being measured

• An ambient temperature compensation circuit to ensure that temperature variations within the IRT, due to ambient changes, are not transferred to the final output.

Sound Level Meters

Sound Level Meter

• Sound level meters measure sound pressure level.

• The reading given by a sound level meter does not correlate well to human-perceived loudness

• A-frequency-weighting filter most common referenced in standards

• Other frequency weightings of C and Z (zero) not as common.

Moisture meters

• measure the percentage of water in a material usually drywall, plaster or wood.

• Identifies if material is unexpectedly wet or dry

• Requires further inspection to identify cause

UV light meterIncident light meter

Light meters

TEMP and RH logger

CO2 monitor

Small Data loggers

Integrated air sampling

Integrated Sampling

Integrated sampling

• Costly requires analytical services• Requires knowledge of suspected contaminant

to identify sampling media• Requires understanding of expected

concentration to identify sampling flow rate and duration

• Not recommended unless a specific contaminant is suspected

• Requires calibration and specialized sample handling

Grab Sampling

Grab VOC Sampling

Passive VOC sampling

Colorimetric and air current tubes

Colorimetric and air current tubes

• Each target analyte has a specific tube designed to change color when compound is present.

• Concentrations are estimated by exposing the tube to a known volume of air usually with a bellows pump.

• Air current tubes are used to track air flow patterns.