chapter 34. cleaning & sterilization

8/11/2019 Chapter 34. Cleaning & Sterilization

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Chemical Indicator (chemical monitor, steri l izer c ontrol, chemical control

device, steri l izat ion-process monitoring device ): A steri l izat ion-process

monitoring device designed to respond with a characterist ic and visible

chemical or physical change to one or more parameters of a steri l izat ion

process.

Chemical Integrator: Chemical indicator that reacts to a variety of

steri l izat ion parameters.

Chemosteri l izer (chemical steri lant): Chemical used for the purpose of

destroying all forms of microbiological l i fe, including bacterial spores. The

same chemical used for shorter exposure periods and/or at a lower

concentrat ion may be used for disinfect ion.

P.957

Cleaning: Removal of foreign material from an item.

Contamination : State of actually or potential ly having been in contact with

microorganisms.

Crit ical I tem: Item that penetrates the skin or mucous membranes or is in

contact with normally steri le areas of the body.

Decontamination : A process that renders contaminated inanimate items safe

for handling by personnel who are not wearing protect ive att ire ( i.e.,

reasonably free of the probabil i ty of transmitt ing infect ion) (2,3,4).

Decontamination can range from simple cleaning to s teri l izat ion.

Disinfectant: Chemical germicide formulated to be used on inanimate objects.

Disinfection: Process capable of destroying most microorganisms but, as

ordinari ly used, not bacterial spores. A disinfectant is usually a c hemical

agent, but some processes (such as pasteurizat ion) are disinfect ing. The

Centers for Disease Control and Prevention (CDC) has adopted a

classif icat ion that includes three levels of disinfect ion.

High-level Disinfect ion : A procedure that ki l ls all organisms with the

exception of bacterial spores and certain species, such as the Creutzfeldt-


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Jakob prion. Most high-level disinfectants can produce steri l izat ion with

suff icient contact t ime.

Intermediate-level Disinfect ion: A procedure that ki l ls v egetat ive bacteria,

including Mycobacterium tuberculosis, most fungi, and viruses but not

bacterial spores (5).

Low-level Disinfect ion : A procedure that ki l ls most vegetat ive bacteria (but

not M. tuberculosis), some fungi, and viruses but no spores (5).

Disposable: Intended for use on one patient during a single procedure.

Fungicide: An agent or process that ki l ls fungi.

Germicide: An agent that destroys microorganisms.

Mechanical Monitor(physical moni to r, ph ysical ind ic ato r): Steri l izer

component that gauges and records time, temperature, humidity, or pressure

during a steri l izat ion cycle.

Noncrit ical I tem: An i tem that does not ordinari ly touch the patient or only

touches intact skin but not mucous membranes (5).

Nosocomial: Pertaining to a health care facil i ty. A nosocomial infect ion is

one acquired in a health care fac il i ty.

Permissible Exposure Limit (PEL): The time-weighted average maximum

concentration of an air contaminant to which a worker can be exposed

according to Occupational Safety and Health Administration (OSHA)

standards.

Prions : Proteinaceous infect ious agents with no associated nucleic acids.

Processing: All of the steps performed to make a contaminated device ready

for patient use.

Pseudoinfection : A posit ive culture without cl inical infect ion.

Pyrogens : Substances that can produce fever.

Reprocessing: Decontamination and repackaging of a device that h as been

used for its intended purpose and is labeled for single use (6).

Resteri l izat ion: Steri l izat ion of an unopened ( i.e., inner wrap st i l l intact,

and therefore, the device is presumably unused) steri le device or an

unused wrapped steri le device that is past the expirat ion date.

Reusable : Intended for repeated use either on the same or different patients,

with appropriate reprocessing between uses.

Sanit izat ion: Process of reducing the number of microbial contaminants to a

relat ively safe level. In general, sanitat ion is used for noncrit ical surfaces or


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for applicat ions in which stronger microbial agents may cause device

materials to deteriorate (4).

Sanitizer: A l ow-level disinfectant.

Semicrit ical I tem: A device that is intended to come in contact with mucous

membranes or in tact skin but wil l no t normally come into contact with steri le

t issues.

Short-term Exposure Limit(STEL): A 15-minute t ime-weighted average

exposure that should not be exceeded at any time during a work day.

Spore: The normal rest ing stage in the l i fe cycle of ce rtain bacteria.

Sporicide: An agent that ki l ls spores.

Standard Precautions : Policies promulgated by the Centers f or Disease

Control and Prevention (CDC) in 1996 that include universal precautions,

airborne precautions, droplet precautions, and contact precautions. Standard

precautions apply to all pat ients, regardless of their diagnosis or known or

presumed infection status.

Steri lant/Disinfectant: Term applied by the Environmental Protect ion Agency

(EPA) to a germicide that is c apable of steri l izat ion or high-level disinfect ion.

Steri le/Steri l i ty: State of being free from all l iving microorganisms. In

pract ice, steri l i ty is usually described in terms of the steri l i ty assurance

level.

Steri l i ty Assurance Level(SAL): Probabil i ty that microorganisms wil l survive

after a terminal steri l izat ion process. Before a manufacturer can label a

product as steri le, i t must have a steri l i ty assurance level of 10 - 6, which

means that the possibil i ty that microorganisms have survived on the item

exists but is no greater than 1 10- 6

or 1 in 1,000,000.

Steri l izat ion: Process capable of removing or destroying all viable forms of

microbial l i fe, including bacterial spores, to an acceptable steri l i ty assurance

level.

P.958

Terminal Steri l izat ion : Steri l izat ion process that is carried out after an item

has been placed in i ts f inal packaging.


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Threshold Limit Value Ceil ing: Concentrat ion of an air c ontaminant to which

it is believed that nearly all workers may be repeatedly exposed day after

day without adverse effect.

Time-weighted Average (TWA): Integrat ion of all the concentrat ions of a

chemical to which a worker has been exposed during a sampling period,

reported as an average.

Transmission-based Precautions: Recommendations by the CDC for patients

with known or suspected infect ion or colonization with highly transmissible or

epidemiologically important pathogens that can be transmitted by airborne or

droplet transmission or by contact with dry ski n or contaminated surfaces.

Tuberculocide : An agent or process that ki l ls tubercle bacil l i .

Universal Precautions : Recommendations made by the CDC that health care

workers consider blood and certain body f luids to be po tential ly infect ious for

bloodborne pathogens and use protective barriers and workplace practices to

reduce the risk of exposure. In 1996, universal precautions were

incorporated into standard p recautions, which expanded the coverage to any

body f luid that may contain contagious microorganisms.

Vegetative : Active growth phase of a microorganism.

Virucide: Agent that inact ivates viruses.

Virus : Submicroscopic, noncellular part icle composed of a protein shell and a

nucleic acid core, and, in c omplex types, a surrounding envelope. In broad

terms, viruses are either l ipophil ic (enveloped) or hydrophil ic (naked) (7).

Role of the Federal Government and Professional

Associations

The EPA registers and regulates chemical germicides (8,9). I t requires

manufacturers to test formulat ions of chemical germicides for microbicidal potency

(eff icacy), stabil i ty, and toxicity. I t also a pproves s teri l izat ion devices.

The Food and Drug Administrat ion (FDA) regulates medical devices and considers

liquid chemical germicides used to reprocess medical instruments as accessories to

medical devices. The FDA requires that the manufacturer of a device marketed as

reusable provide the user with adequate instruct ions for cleaning and disinfect ing

or steri l izing the item.

In 1993, the FDA and EPA signed a memorandum of understanding that states that

the agencies wil l divide the premarket clearance of germicides so that the FDA


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would clear liquid chemical sterilants and the EPA would register general-purpose

disinfectants before marketing (9A).

OSHA regulates occupational exposure to chemical disinfectants and steri l izers.

The CDC does not approve, regulate, or test germicides or s teri l izers. Rather, i t

recommends broad strategies to prevent transmission of infect ions in the health

care environment.

Practices and procedures to reprocess reusable devices have been published by

several professional organizations, including the American Society of

Anesthes iolog is ts (ASA), the Ame ric an As sociati on of Nurs e Anesthetis ts (AANA ),

and the Associat ion of Operating Room Nurses (AORN) (2,10 ,11).

Resistance of Microorganisms to Disinfection andSterilization

Microorganisms can be categorized into groups according to their innate resistance

to a s pectrum of physical processes o r chemical germicidal agents. Figure 34.1

shows a general descending order of microbial resistance levels. Resistance to

disinfect ion and steri l izat ion is not equivalent to resistance to antibiot ics. For

example, antibiot ic-resistant strains of staphylococci do not appear to be more

resistant to chemical germicides than nonresistant bacteria (8).

Cleaning

The f irst and most important step in decontamination is thorough cleaning

(12,13,14). In s ome cases, cleaning may be suff icient to render an i tem suitable for

reuse. I f an art icle is not c lean, retained salts and organic soil could inactivate

chemical germicides or protect microorganisms during the disinfect ion or

steri l izat ion process. Even if the item is rendered steri le, residues may interfere

with the device's function or cause a reaction in a patient.

I t is important to prevent blood or other body f luids from drying on devices.

Enzymatic foam sprays that prevent drying, break down blood and protein, and

inhibit bacterial growth are available. Flushing lumens with enzymatic cleaner wil l

break up debris. I tems that can be immersed should be soaked in water plus an

enzyme presoak with or without detergent for at least 3 minutes (15 ). Stainless

steel or other metal devices should not be soaked in saline or s odium hypochlorite

solut ions, because the chloride ions in these two s ubstances wil l cause the metal to

corrode (13). A c losed container should be used to move contaminated devices to

the decontamination area.


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P.959

View Figure

Figure 34.1Descending order of resistance of organisms.

Cleaning should be performed in a designated location that is separate from other

parts of the facil i ty to minimize inadvertent personnel exposure or exposure of

other items to contaminants. The area sh ould be restricted to authorized personnel

as much as possible. I t should be away from traff ic, pat ients, and clean-item

storage. The f loors, walls, ceil ing, and work surface should be made of non-porous

materials that wil l not s upport the growth of mold. These surfaces should be

washed frequently. The area should have adequate lighting with no shadowed or

dark areas. The f loor should be designed to prevent sl ipping but be easy to clean.

Horizontal work surfaces should be cleaned and disinfected daily. Fluid spil ls

should be cleaned up quickly to prevent sl ips and falls. I f the spil led material was

contaminated with blood, the spil l area should be treated after it has been cleaned

up with a tuberculocidal germicide.

The heating, venti lat ion, and air-condit ioning systems should be designed to

minimize spreading contaminants to adjacent spaces. The air pressure within the

decontamination space should be negative relat ive to the surrounding spaces so

that air does not f low out of the area. There should be a minimum of 6 to 10 total

air exchanges each hour with 100% fresh air. Air from this area should be

exhausted to the outside without recirculat ion or to a f i l tered part ial recirculat ing

system.


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The area should be divided into dirty and clean areas. Signs showing where dirty

equipment is to be placed should be prominently displayed. Sinks should be big

enough to contain large instruments, and there should be enough sinks to

accommodate concurrent soaking, washing, and rinsing. Sinks should have

attached c ounters or adjacent work surfaces on which to place soiled and clean

items separately. Hand-washing facil i t ies s hould be conveniently located in or near

the decontamination area. Personnel should wear a full complement of protective

attire (hair covering, fluid-resistant mask, eyewear, waterproof gown or apron,

appropriate gloves, and waterproof shoes or boots with n onskid soles) (13 ,16 ).

Personnel should be careful not to injure themselves with contaminated

instruments.

Each device manufacturer's instruct ions should be c onsulted to determine the

appropriate cleaning methods and agents to remove soil without damaging the

device. Tape should be removed and adhesive residue dissolved by using an

appropriate solvent.

P.960

The next step is disassembly (if not done at the source). An init ial water r inse or

soaking with a specialized product (e.g., a protein-dissolving solut ion) can prevent

blood coagulat ion on the device and remove gross debris. The water temperature

should not exceed 45C, because higher temperatures cause proteinaceous soil to

coagulate (17). An alternative is to use a spray-on precleaner to help dissolve the

soil (12).

Af ter the equipm ent has soa ked long eno ugh to loosen orga nic matte r, i t should be

thoroughly sc rubbed inside and out. Part icular attention should be paid to lumens,

crevices, corners, grooves, and knurled or textured surfaces. I t is important to have

a variety of brushes (18 ). Brushes and other cleaning implements should be

disposable or should be cleaned and steri l ized or undergo high-level disinfect ion at

least daily.

Immersible devices cleaned under water to prevent aerosolizat ion of

microorganisms. A cloth soaked i n detergent and water can be used to clean items

that cannot be immersed. Detergents should be low s udsing and rinse off without

leaving a residue. Detergent residues can lead to staining and may interfere with

the act ion of some chemical disinfectants (13).


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Cleaning may be accomplished manually, mechanically, or by a combination of

both. Using mechanical equipment may increase productivity, improve cleaning

effect iveness, and offer greater protect ion for the worker.

A varie ty of wa shing machines are avai la ble (12,19 ). They are highly automated,

usually with microprocessor control. Washer-steri l izers are designed to wash, r inse,

and then steam steri l ize items (4,13). Washer-decontaminators/disinfectors use hot

water in the range of 60C to 95C. They are designed to wash, r inse, and dry the

same items as a washer-steri l izer but can process items that would be deteriorated

by the high temperature used in steam s teri l ization.

Some equipment that has joints, c revices, lumens, and other hard-to-reach areas

can be treated in an ultrasonic cleaning system after gross soil has been removed.

In an u ltrasonic cleaner, high-frequency sound waves passing through a solvent

produce submicroscopic bubbles. These bubbles collapse on themselves,

generating t iny s hock waves that knock debris off surfaces. A detergent is often

added to the ultrasonic l iquid. The water may be heated. Ultrasonic cleaning tanks

are available in a variety of si zes and configurat ions. The equipment to be cleaned

is placed in a basket or tray and into the ultrasonic tank for a preset period of

t imeusually 3 to 6 minutes. Ultrasonic cleaning monitors are available (20 ). Some

manufacturers of delicate instruments, including laryngoscopes, recommend that

they not be subjected to ultrasonic cleaning because the process may loosen f ine

screws and adversely affect alignment (21).

Af ter c lea ni ng , ri ns ing shou ld be perf ormed to remove soil an d re sidual de terg en t

and to keep i t from resett l ing on the equipment. Lumens and channels should be

well f lushed during each rinse. Inadequate rinsing can cause irr itat ion and burns in

patients (22 ). Some items (such as those undergoing plasma sterilization) should

be rinsed with alcohol or dist i l led or demineralized water.

The cleaned item should be thoroughly dried. Even if an item is to undergo no

further processing, drying is important because a humid environment may

encourage the growth of certain organisms. I f a l iquid chemical agent is to be used,

water on the equipment will dilute the agent and make it less effective. If water

droplets remain on equipment that is to be gas steri l ized, ethylene oxide (EO) wil l

dissolve in the water and form ethylene glycol, which is both toxic and dif f icult to

remove. Most items may be towel- or air-dried. Air-drying cabinets and hot-air

ovens are available (Fig. 34.2). If an item is to undergo EO sterilization, unheated

air should be used.


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Af ter c lea ni ng , each i tem shou ld be in spec te d to verif y c lean li ness and te ste d fo r

functionality (23). All accessible surfaces should be examined under normal

l ight ing. Swab tests for detect ing residual protein on surfaces are available.

Disassembled devices must be reassembled to perform functionality testing. After

functionality is verif ied, some devices must again be disassembled to ensure that

the steri lant can contact all the surfaces.

Disinfection and Sterilization Methods

Pas t e u r i z a t i o n

With pasteurization (hot water disinfection), the equipment is immersed in water at

an elevated temperature (but below 100C) for a specified time. The time and

temperature va ry. A typical sequence is 30 minutes at a temperature of 70C.

Contact time is inversely related to temperature, that is, for equivalent microbial

ki l l , a longer exposure t ime is required when the temperature is reduced. CDC

guidelines refer to p asteurizat ion as a high-level disinfect ion process, although

some feel i t is intermediate-level (13,24 ).

Pasteurizing machines come in dif ferent sizes ( Fig. 34.3). Many also wash the

equipment. They are simple to load and operate. Special dryers that a re equipped

with f i l ters are available.

Pasteurization has been used for breathing tubes, reservoir bags, tracheal tubes,

face masks, airways, laryngoscope blades, stylets, bi te blocks, Y-pieces, elbows,

adaptors, and venti lator bellows.

A ma jor advan tage of pas teurizat ion is that the lowe r te mp era tu re is les s damagi ng

to equipment than the higher temperatures employed during autoclaving. There are

no toxic fumes or residues. I t is simple,

P.961

inexpensive, and reliable. This technology may result in considerable savingscompared with throwing equipment away. The main disadvantage is that the treated

equipment is wet and must st i l l be dried and packaged, during which t ime it may

again become contaminated. The heat may damage some materials.


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View Figure

Figure 34.2Forced-air drying cabin for equipment. (Picturecourtesy of Olympic Medical.)

S t eam St e r i l i z a t i o n

Steam steri l izat ion (autoclaving) ut i l izes saturated steam under pressure

(19,25,26,27 ,28 ,29). I t is the most widely used and inexpensive of the steri l izat ion

techniques.

At sea le vel , wa ter boils at 100C . Whe n it is boi led wi thin a clo sed vessel at

increased pressure, the temperature at which it boils and that of the steam it forms

will exceed 100C. The increase in temperature depends on the pressure within the

chamber. Pressure per se has l i t t le or no steri l izing effect. I t is the moist heat at a

suitable temperature, as regulated by the pressure in the c hamber, that b rings

about steri l izat ion.

Increasing the temperature dramatically reduces the t ime needed to achieve

steri l izat ion. The minimum t ime for steri l izat ion by steam at 121C is 15 minutes. I f

the temperature is 126C, the t ime is reduced to 10 minutes.

P.962

It is 3.5 minutes at 134C and only a few seconds at 150C.


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View Figure

Figure 34.3Pasteurization machine. (Picture courtesy ofOlympic Medical.)

Increasing the temperature dramatically reduces the t ime needed to achieve

steri l izat ion. The minimum t ime for steri l izat ion by steam at 121C is 15 min. I f the

temperature is 126C, the time is reduced to 10 min. It is 3.5 min at 134C and only

a few s econds at 150C.

Autoc lav in g is ef fecti ve because the s te am tra nsfers he at to ma te rials ra pi dl y on

contact. Microbial destruct ion wil l be most effect ive at locations where saturated

steam can contact the microorganisms. At locations inaccessible to steam

penetrat ion (as might occur with complex devices, improperly packaged items or

incorrect load configurat ions), some microbial destruct ion may occur, but dry heat

is not as eff icient at steri l izing as saturated steam.

Equipment to be steri l ized is cleaned, and then may be packaged in a material

easily penetrated by steam. After steri l i zat ion, the packaging material prevents

recontamination during subsequent handling and storage.

P.963

Autoclave Design

A ste am ste ri l ize r can ran ge f ro m a sma l l , manually-operate d table to p s te ri l ize r to a

large, computer-controlled, f loo r-loading model (26 ,28,29 ,30 ,31). Steri l izers are

described by the method of air removal, temperature and the time the chamber is

held at the specif ied temperature (e.g., vacuum, 130C, 4 minutes) (28 ).


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The chamber (pressure vessel) is where materials to be steri l ized are placed and

through which steam is circulated. I t must be c onstructed to withstand the high

pressures required to bring the steam up to the temperatures required and f it ted

with a safety valve to prevent development of excessive pressure. Chamber size

varies from less than 1.5 cubic feet in small tabletop steri l izers to more than 70

cubic feet in large f loor-loading models (28 ). The jacket is the port ion surrounding

the chamber. It functions to maintain the temperature in the chamber.

The steri l izer may be equipped with one or two doors. Doors may be hinged or

sliding and are opened and closed manually or by power (electric, pneumatic or

hydraulic). I tems are placed on a shelf in the chamber, and the door closed and

secured.

Ai r must be dis placed f ro m th e chamber. Thi s is called th e cond iti oning or hea t- up

phase (Figure 34.4). I ts length varies, depending on the load. In the gravity-

displacement type of s teri l izer the incoming steam displaces the air through a port

or drain in or near the bottom of the chamber. The steri l izer chamber drain remains

open unti l the temperature in the drain is the same as the t emperature of the steam

entering the chamber, indicating that the air has been removed. The pre-vacuum

steri l izer depends on one or more pressure and v acuum excursions to remove air.

The steam-flush pressure-pulse steri l izer uses a repeated sequence of a steam

flush and a pressure pulse. No vacuum is required. A pre-vacuum or steam-flush

pressure-pulse steri l izer results in shorter cycles because air is removed more

rapidly.

In the gravity-displacement type of steri l izer, the incoming steam displaces the air

through a port or drain in or near the bottom of the chamber. The steri l izer

P.964

chamber drain remains open unti l the temperature in the drain is the same as the

temperature of the steam entering the chamber, indicat ing that the air has been

removed. The pre-vacuum steri l izer depends on one or more pressure and vacuum

excursions to remove air. The steam-flush pressure-pulse steri l izer uses a repeated

sequence of a steam f lush and a pressure pulse (Fig. 34.4). No vacuum is required.

A prevac uum or s team-flus h pres sure-p ulse s te ri l izer re sul ts in shorter cycles

because the air is removed more rapidly.


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View Figure

Figure 34.4Typical steam sterilization cycle. Conditioningphase (A); sterilization phase (B); exhaust phase (C); dryphase (D). (Redrawn from a figure inYoung JH. Steam sterilization: scientific principles. In:Reichert M, Young JH, eds. Sterilization Technology forthe Health Care Facility. 2nd ed. Gaithersburg, MD: Aspen

Publishers, Inc., 1997:124133.)

As steam ente rs the chamber, i t en te rs the load to be ste ri l ize d an d gi ves up i ts

latent heat. Once the intended temperature is reached, the sterilization time is set.

This is called the exposure o r steri l izat ion phase . By convention, steri l izat ion

cycles in health care sett ings have been s tandardized at a few temperature-t ime

relat ionships (29 ). The lowest temperature for a steri l izer is 121C (250F). Cycles

may also be programmed at 132C (270F), 134C (275F), or 145C (285F),

depending on the steri l izer. In general, wrapped items should be steri l ized for 30

minutes and unwrapped items for 20 minutes at 121C ( 32).

Af ter the s te ri l iza t ion phas e, i tems mus t be dried bef ore being remov ed from the

steri l izer. This is called the pos texposure (exha us t, dry) phase and consists of

exhausting the chamber to atmosphere followed by circulat ing f i l tered air through

the chamber or by drawing a deep vacuum (27). Some tabletop autoclaves require

that the door be c racked, but newer models may allow closed-door drying (33,34 ).

Flash steri l izat ion allows items to be s team steri l ized for immediate use (35 ,36 ).

The items to be processed are usually unwrapped. The time and temperature will

depend on the steri l izer and the configurat ion of the load. The processed items are

transferred immediately from the autoclave to the point of use, usually the steri le

f ield in an ongoing surgical procedure.

Problems with Steam Sterilization

P r o b l em s w i t h t h e St e am


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Steam quality or saturation refers to the percentage of liquid in steam. Current

standards call for a steam quality greater than 97% (less than 3% liquid water).

Variations in steam pressure may affect the time needed to attain the proper

temperature and temperature uniformity within the chamber. Clogged f i l ters, poorly

engineered piping, or excessive demands on the steam supply may cause pressure

variat ions. Steam is saturated when it has the proper balance of pressure and

temperature. I f the pressure is too high, the steam wil l change to l iquid, c ausing

packs to become wet; i f the pressure is too low, the s team wil l be superheated.

Superheated steam is less able to transfer its heat e nergy to the cooler items being

steri l ized than saturated steam and wil l interfere with achieving a uniform

temperature in the chamber.

A i r i n t h e A u t o c l a v e Ch amb e r

The presence of air in the chamber wil l impair steri l izat ion. Air conducts heat poorly

and retards steam penetration. The autoclave evacuates much of the air at the

beginning of the cycle (Fig. 34.4). All of the air does not have to be removed, but

all surfaces requiring steri l izat ion must be exposed to adequate moisture (27 ).

Improper steri l izer loading and incorrect ly prepared individual packages can affect

the abil i ty of the steri l izer to remove air from the load (37 ).

Many autoclaves have a built- in vacuum leak test ( 37 ). Such steri l izers are c apable

of running a special c ycle that pauses when the maximum vacuum is achieved. For

others, the eff icacy of the air removal process can be tested by a Bowie-Dick test.

This is run with a s ingle test pack in the chamber. This should be run each day

before the f irst steri l izat ion cycle (20 ,38). Air detection devices may be added to

the steri l izer plumbing and c ontrol system.

E q u i pm e n t M a lf u n c t i o n

Examples of equipment malfunction include out-of-calibration temperature or

pressure gauges and controllers, incorrect steam supply pressure, faulty or

maladjusted control valves, leaks, clogged vent l ines or drain screens, faulty

vacuum pumps, defect ive steam traps, and malfunctioning cycle sequence

controllers.

Per s o n n e l E r r o r s

Personnel errors include inadequate cleaning, incorrect pack preparation o r

packaging methods, and poor loading techniques (39). I tems in the steri l izer must

be posit ioned so that air c annot be trapped. I tems should not be crowded or stuffed


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into the autoclave. Crowding may interfere with both air el imination and drying. I f

the shape of an item would allow water to collect in any part, that item should be

posit ioned on its side or upside down so that the water can run out. I f water can

pool, then air could be trapped against the surface.

Steam Sterilization Monitoring

Steri l izat ion validat ion is achieved by using a c ombination of mechanical, chemical,

and biological indicators (19 ,40). Using these in concert wil l g ive the greatest

possible confidence that items are s teri le.

Me c h a n i c a l I n d i c a t o r s

Mechanical monitors indicate time, temperature, and pressure (37 ). Most

autoclaves provide a permanent record of these parameters. The temperature in a

f loor-loading steri l izer is typically measured in the chamber drain piping. In small

tabletop steri l izers where the s team is generated within the chamber, the

temperature is usually measured in the chamber. Some tabletop steri l izers do not

have a recorder. With

P.965

these, it is important to monitor physical condit ions during the cycle (39 ).

View Figure

Figure 34.5Autoclave tape is an example of an externalprocess indicator. The exposed tape is at top.

Ch em i c a l I n d i c a t o r s

Chemical indicators are divided into f ive classes (41 ,42,43,44). The higher the

class, the more sensit ive the indicator.


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Class 1 i ndicators are i nternal and external process indicators. These inform the

user that the item has been exposed to the steri l izat ion process. The most common

example of an external process indicator is autoclave tape (Fig. 34.5). Most tapes

do not respond to al l the parameters of steri l izat ion but do offer visual proof that

the pack has been through the process. Internal process indicators usually exhibit a

color change from white to black. Like autoclave tape, they have l imi ted sensit ivity

to the parameters of steri l izat ion but do i ndicate exposure to steam.

Class 2 i ndicators relate to the Bowie-Dick test for vacuum steam steri l izers. They

do not determine if the steri l izat ion parameters have been met but only assess

vacuum pump efficiency and detect the presence of air leaks and/or gases in the

steam. The indicator is placed in a pack of towels (handmade or purchased) on the

front bottom shelf over the drain and a 3.5- to 4 -minute cycle is run. Many new

steri l izers are equipped with leak test c ycles, so these indicators do not need to be

used.

Class 3 i ndicators are si ngle parameter. An example is the temperature tube that

contains a chemical that melts and sometimes changes color when the appropriate

temperature is attained. These indicators are helpful in determining if the

appropriate temperature was achieved in the center of large packs. False-positive

results have been reported (43).

Class 4 i ndicators respond to one or more steri l izat ion parameters. They contain an

ink that changes color when exposed to the correct combination of s teri l izat ion

parameters.

Class 5 i ndicators are also known as integrat ing indicators or integrators. They

respond to all parameters of steri l izat ion over a specif ied range of temperatures.

False-posit ive and false-negative results have been reported (41 ).

Chemical indicators can detect fai lures or errors in packaging, pack density,

loading, insufficient humidification, inadequate exposure time at the selected

temperature, or sterilizer malfunction. An important advantage is that they can be

read as soon as the packs have been opened. Another advantage is that they are

so inexpensive that one can be used in every pack.

The CDC and a ll major U.S. o rganizations that issue steri l izat ion-related standards

or guidelines advocate that a chemical indicator be attached to every package that

goes through a steri l izat ion cycle and within e ach package to be steri l ized in what

is expected to be the most dif f icult-to-steri l ize location.

There are both U.S. (45,46 ,47 ) and international (48 ,49,50,51,52,53) standards for

chemical indicators.


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B i o l o g i c a l In d i c a t o r s

Biological indicators are standardized preparations of spores (typically str ips or

ampoules) that are placed in the most dif f icult-to-steri l ize location(s) in the load

(37,43). Alternatively, a biological indicator that is enclosed in a commercial test

pack can be used. The indicators are exposed to the steri l izat ion cycle, retr ieved,

incubated, and examined for microbial growth. A posit ive b iological indicator is

indicat ive of a possible steri l izat ion process failure. Commercial mail- in biological

monitoring services eliminate the need for on-site incubation.

One type of b iological indicator contains a rapid detect ion system that is based on

the interact ion of an enzyme in the bacterial spore with a substrate in the growth

medium. Fluorescence occurs when the viable biological indicator is exposed toultraviolet light. This type of indicator can be read in 3 hours with a wrapped item

or in 1 hour with an unwrapped item. It may be particularly useful in the operating

or ambulatory sett ing where products are often steri l ized unwrapped in a gravity

displacement steri l izer (43 ,54).

The main problem with biological indicators is the t ime needed for incubation.

Biological monitors should be used at least once a week but preferably daily a nd

after major repairs to the steri l izer ( 37,43 ).

There are both U.S. (55,56 ,57 ,58,59 ) and international (60,61,62,63) standards for

biological indicators.

Advantages and Disadvantages of Autoclaving

Steam autoclaving can kil l al l bacteria, viruses, and spores. Advantages include

speed, good penetrat ion, economy, ease of use, absence of toxic products or

residues, and reliabil i ty. The material can be prepackaged and kept steri le unti l

used. I t poses no harm to

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the environment. A major advantage is that at least one autoclave is available in

every modern operating theater.

The principal disadvantage of autoclaving is t hat many pieces of equipment are

damaged if subjected to steam. Autoclaving can cause blunted cutting edges, metal

surface corrosion, and shortened l i fe of electronic components. Fiber-optic

laryngoscope blades show a decrease in l ight transmission with repeated

autoclaving (64 ).

Dry Hea t St e r i l i z a t i o n


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Dry heat is used for items that might be damaged by moist heat ( 65 ,66 ,67 ). While

slow, this technique penetrates well and does not corrode metal and sharp

instruments (68 ). I t is useful for nonaqueous l iquids or semisolids such as talc,

glycerin, oils, petroleum jell y, waxes, and powders.

Times and temperatures frequently used for dry heat steri l izat ion are 170C for 60

minutes, 160C for 120 minutes, and 150C for 150 minutes (32 ,68). Some of the

newer dry heat steri l izers can attain temperatures up to 210C (65). Convection hot

air steri l izers improve heat transfer by using forced air. These units have

comparatively fast cycle t imes.

There are both U.S. and international standards for biological indicators for dry

heat steri l izat ion processes (69).

Chem i c a l D i s i n f e c t i o n and S t e r i l i z at i o n

Chemical (cold) disinfect ion/steri l ization involves immersing an item in a solut ion

that contains a disinfectant (3). This method is especially useful for heat-sensit ive

equipment. I t can be accomplished by automated equipment, which typically

provides a cycle of cleaning, r insing, disinfect ion, r insing, and sometimes drying.

Regulation and Labeling

The EPA regulates formulat ions and labeling of c hemical germicides (70). The

labeling must p rovide c ertain information, including precautionary statements,

directions for use, the required contact time, recommended use temperature, use

pattern, use l i fe, and shelf l i fe. The EPA also requires that the label show the

abil i ty of the chemical agent to destroy certain organisms such as M. tuberculosis.

I t is imperative that the user str ict ly fol lows the direct ions provided by the

manufacturer.

The FDA clears l iquid chemical steri lants. The current l ist ing of cleared l iquid

chemical steri lants and the t ime-temperature claims for steri l izat ion and high-level

disinfect ion can be accessed at http://www.fda.gov/cdrh/ode/germlab.html .

Factors Influencing Chemical Disinfection

Co n c e n t r at i o n o f t h e Ch em i c a l

In general, higher concentrat ions of the ac t ive ingredients increase the

disinfectant 's bactericidal abil i ty. An exception is the alcohols. However, extremely

high concentrat ions increase the potential for damage both to inanimate objects

and to the sk in and mucous membranes of p ersonnel. For best results, products

should be used according to the manufacturer's recommendations.
http://www.fda.gov/cdrh/ode/germlab.htmlhttp://www.fda.gov/cdrh/ode/germlab.html


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Water left on equipment wil l di lute the chemical and render it less effect ive. Dilut ion

can become signif icant with frequent reuse and can reduce the concentration to a

level that is too low to be effect ive. For this reason, equipment should be dried

before undergoing chemical disinfect ion or s teri l izat ion. In some cases, the

technique (manual or automatic) may determine how fast the co ncentrat ion falls

(71).

Tempe r a t u r e

Higher temperatures usually increase the effect iveness of chemical agents. Special

devices are available for heating some chemical solut ions. Too high a temperature

may cause the act ive ingredients to evaporate or degrade. The label should tell

which temperature should be used.

E v a p o r a t i o n a n d L i g h t D e ac t i v a t i o n

I f the solut ion is in an uncovered container, evaporation can occur. Usually,

evaporation is not as serious as dilut ion. However, i f the chemical agent is more

volat i le than the diluent, loss by evaporation can be very important. Chlorine

products are especially susceptible to evaporation and deactivat ion from exposure

to l ight.

B i o b u r d e n

In general, the higher the level of microbial contamination, the longer the exposure

to the chemical germicide necessary before the entire microbial populat ion is ki l led.

Thus, items should be scrupulously cleaned. Liquid agents vary widely in their

effect iveness against various types of microorganisms. Table 34.1shows the

capabil i t ies of s ome commonly used agents.

p H

The relat ive acidity or alkalinity of disinfectants can inf luence the biocidal act ivity.

An inc reas e in pH tends to decre as e the eff icac y of ph eno ls, iod ine , and

hypochlorites. In contrast, i t wil l improve the antimicrobial act ivity of glutaraldehyde

and quaternary ammonium compounds. Soluble c alcium or magnesium in the water

supply can react with detergents to form insoluble precipitates, which tend to

neutralize some disin-fectants (4).

Ch a r a c t er i s t i c s o f t h e It em t o B e D is i n f e c t e d

A dis inf ecta nt so lu ti on wi l l be effec ti ve on ly if i t can con tac t al l surfa ces (inn er an d

outer) of the item to be disinfected (72 ). Uneven or porous surfaces resist chemical

disinfect ion. Air


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entrapment can prevent contact between the liquid and parts of the device.

TABLE 34.1 Capabilities of Disinfecting Agentsa,b

Disinfectant Gram-

Positive

Bacteria

Gram-

Negative

Bacteria

Tubercle

Bacillus

SooresVirususFungi

Quaternary ammonium

compounds

+ 0 0

Alcohols + + + 0

Glutaraldehydes + + + + +

Hydrogen peroxide-based compounds

+ + + + +

Formaldehyde andother agents

+ + + - + +

Phenolic compounds + + 0

Chlorine + + + - + +

aFrom Chatbum RL. Decontamination of respiratory care equipment what can be

done, what should be done. Respir Care 1989:34:98; and Berry AJ. Infection control in

anesthesia. Anesth Clin North AM 1989;7:967981.

b+, good; , fair, 0, little or none.

Use Pa t t e r n , U s e L i f e , an d S t o r a g e L i f e


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The product label should be examined for information on the use pattern, use l i fe,

and storage l i fe. Use pattern refers to how many t imes the solut ion can be used.

Use l i fe commonly applies but is not l imited to disinfectant products that applies,

but is not l imited to, require mixing of two ingredients for act ivat ion. Once a

disinfectant solut ion is mixed, there wil l be a l imited period of t ime during which the

activated solut ion may be used. The container should be marked with the date the

solut ion was prepared and the date it expires. The storage l i fe is the t ime period

after which the u nused and/or unactivated product is no l onger deemed effect ive.

T im e

The t ime required for dif ferent chemical agents to function effect ively varies from

seconds to hours and wil l depend on the factors just mentioned. Somemicroorganisms are killed faster than others. Contact time may make the difference

between steri l izat ion and high-level disinfect ion. For high-level disinfect ion, a

minimum contact t ime of 20 to 30 minutes is recommended (3). A lower level of

disinfect ion can be achieved in less t ime. Leaving devices in the disinfectant too

long can make it harder to r inse off the chemical (22 ).

Safe Practices

Designated areas for chemical disinfect ion s hould be strongly encouraged

(2,5 ,73 ,74,75,76,77,78,79,80,81 ). Ideally, the area used for cleaning should beseparate from the space where the chemical is used. Both of these spaces should

be separate from patient p rocedure and personnel support areas. Traff ic should b e

limited to trained personnel.

Chemical disinfectants should be used in an area that is large enough to ensure

adequate vapor dilution with an air exchange rate not less than 10/hour. The fresh

air inlet should be p laced across the room from the local exhaust venti lat ion.

Local exhaust venti lat ion (either a ductless system or a ducted fume hood) should

be installed to capture chemical vapors. A ducted fume hood should be connected

to a non-recirculat ing exhaust system that goes to the outside atmosphere at a

location away from people and air in take ducts. Self-contained (ductless) fume

hoods (Fig. 34.6) encapsulate the soaking container and have a blower that draws

fumes away from the operator and delivers them to a s ystem that chemically

inactivates the germicide and returns clean f i l tered air to t he room. This eliminates

the need to install a duct.

The employer should provide training to each employee who handles germicides

and verify that each employee has received and understood the required training.


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Automated processing equ ip ment can reduce ex posure to ge rm icides. Hoods

designed for automatic washing machines are available.

Personnel should wear appropriate protective equipment designed to protect the

skin, eyes (goggles or ful l face shields), and clothing from splashes when using

chemical germicide solut ions. Impervious gloves and gowns should be worn. T he

user should double glove and/or change single gloves frequently. Protect ive

clothing should be removed quickly if i t becomes saturated and should be

laundered before reuse. There should be ready access to means to decontaminate

the eyes and skin in the event of contact with the solut ion.

During preparation and act ivat ion of germicide solut ions, every effort should be

made to minimize splashing, spil l ing, and personnel exposure. The chemical should

be kept in a closed container with a t ight-f i t t ing l id. Agitat ion and splashing should

be avoided when the solut ion is poured. Safety nozzles can be used to

P.968

reduce the exposure to v apors created when pouring solut ions.

View Figure

Figure 34.6Glutaraldehyde user station. Fumes are drawnaway from the operator and into a filter, where they areneutralized.

I f i t is necessary to transport an act ivated solut ion, a method of transportat ion that

wil l minimize the potential for spil ls and the possibil i ty of personnel exposure to the

solut ion or vapor should be selected. Transport ing solut ions in containers such as

trays or buckets should be av oided.

The disinfectant solut ion should be stored in a t ight ly closed container in a well-

ventilated area. Containers that minimize the surface area should be used. The lid


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should be kept on the c ontainer at a ll t imes except when items are placed i nto or

removed from the solut ion.

Items should be immersed in the chemical solut ion gently, taking care to disturb

and agitate the surface as l i t t le as possible. When the solut ion must be manually

irr igated or f lushed through internal channels or lumens, care should be taken to

avoid splashing. The syringe should be carefully f i l led with the solut ion and

securely attached to the channel opening or all-channel irr igator and the solut ion

pushed slowly.

Items should be gently removed from the solution and rinsed thoroughly in clean or

steri le water. Rinse water should be discarded promptly, not reused. Semicrit ical

items should be rinsed with steri le water to prevent organisms that may be in tap

water from contaminating them. Alternately, the items may be rinsed f irst with tap

water and then with alcohol.

Discarding a chemical solut ion involves high risk of employee exposure. The

solut ion should be discarded, along with copious amounts of c old water into a drain

connected to a sanitary se wer. Chemical germicide solut ions should not be

discarded into septic s ystems.

A spi ll conta inment re spon se team shou ld be created and be res po ns ible for

developing and executing procedures for chemical spil ls. I f there is a chemical that

can be used to neutralize the germicide and reduce ambient vapor levels in spil l

situat ions, it should be readily available.

Small spil ls and droplets can be absorbed and neutralized by using special mats

that are highly absorbent and treated with the neutralizing chemical. Alternately,

they can be wiped up quickly with a sponge, towel, or mop that has been

neutralized with an appropriate chemical agent and then wiped up. The sponge,

towel, or mop should be thoroughly r insed with large amounts of water and the

water discarded through the drain.

Larger spil ls are best treated by using chemical spil l kits that include an approved

deactivator/neutralizer to pour over the spil l . Personnel should wear suitable

protect ive att ire. The spil l should be contained and neutralized or co ntained and

collected for disposal. After the solut ion is removed, the area where the solut ion

was collected should be thoroughly r insed. The cleanup tools should be rinsed with

a large amount of water and the water discarded down the drain.

To ensure a safe work environment and establish compliance with recommended

limits and guidelines on occupational exposure to germicides, several air sampling

and monitoring techniques can be used. Sampling should be conducted in all areas


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where workers might be exposed to vapor. Monitoring should be conducted during

normal use and whenever there is a major change in protocol, workplace

venti lat ion, case load, or major repair to washers or other automated equipment.

Special attention should be given to periods of time when airborne concentrations

of vapor might be particularly high (e.g., when the worker is pouring the spent

solut ion down the drain or pouring fresh solut ion into a container). Monitoring

should be documented and records maintained.

Exposure can be determined by using a sampling pump to pull a known quantity of

air through a tube containing an absorbent medium. This is analyzed later by

P.969

an industrial laboratory. A passive monitoring badge can be worn by personnel. The

germicide vapor is converted into a s table derivat ive and analyzed.

Monitoring Chemical Disinfection

Standard biological preparations are available only for steri l izat ion processes and

cannot be applied to disinfect ion. The only way to assess the lethality of

disinfect ion is to use the direct-assay steri l i ty test of the f inished product (4). This

test is dif f icul t and t ime consuming, renders the tested object unusable unti l i t is

subsequently recleaned and decontaminated, and is relat ively insensit ive in its

abil i ty to detect low-level contamination.

Because disinfect ion procedures cannot be effect ively monitored biologically, they

must be monitored physically. Records indicat ing exposure t ime, temperature, and

pressure (if applicable) should be maintained.

Agents

No chemical germicide is suitable for all purposes. A number of factors should be

considered in select ing one, including the degree of microbial death needed; the

nature and composit ion of the item being treated; whether the i tem is crit ical,

semicrit ical, or noncrit ical; and the cost, safety, and ease of use. Antiseptics are

not appropriate for disinfect ing inanimate surfaces or objects.

G l u t a r a l d e h y d e

Glutaraldehyde-based solut ions have been widely used because of their excellent

germicidal propert ies, act ivity in the presence of organic matter, noncorrosiveness

with most equipment, and lack of coagulation with proteinaceous material

(3,5 ,8,68 ,70 ,82,83 ,84). Glutaraldehyde has an ex tensive shelf l i fe. I t may be us ed


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as long as 30 days after act ivat ion, provided in-use dilut ion and organic stress are

properly controlled.

Glutaraldehyde is effect ive against bacteria, fungi, and vi ruses at room

temperature. High-level disinfect ion requires 20 to 30 minutes ( 85 ,86,87 ,88 ). I t is

also sporicidal, provided adequate t ime is allotted. Three to 10 hours are required

for steri l izat ion. Elevating the temperature can shorten these t imes (89 ). The

manufacturer's instruct ions should a lways be c onsulted.

Dilut ion often occurs during use, and it is important to ensure that equipment is

disinfected with an acceptable concentration of agent. Glutaraldehyde

concentrat ion test s tr ips that are dipped into the solut ion to determine the act ive

concentrat ion are available. Problems with these str ips have been reported (90). It

is generally recommended that 1% t o 1.5% glutaraldehyde be the minimum

concentrat ion for high-level disinfect ion ( 88). Solut ion concentrat ion should be

monitored at least once every day and a log kept of each test (81).

A wide vari ety of bra nd -name products is av ai la ble . Th ey d if fe r pri ma rily in the

concentrat ion of glutaraldehyde and addit ives. Most aqueous solut ions are acidic

and must be ac t ivated (made alkaline) to become sporicidal (Fig. 34.7). Acid

glutaraldehydes are available and do not require act ivat ion, but some studies have

shown them to have less microbiocidal act ivity than alkaline preparations (88). The

pH needs to be between 7.5 and 8.5 to be sporicidal (5).

View Figure

Figure 34.7Glutaraldehyde. The small container containsthe activator, which must be added to the contents of thelarge container.


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Glutaraldehyde solut ions ev aporate at room temperature. Exposure to

glutaraldehyde can result in a va riety of reactions in health care workers, including

headaches; skin, eye, and mucous membrane irr itat ion; and asthmalike symptoms

(91,92,93,94 ). Salivary gland enlargement attributed to oropharyngeal airways

inadequately r insed after exposure to glutaraldehyde has been reported (95 ). These

symptoms are usually temporary and subside when the individual leaves the area of

exposure but may be exacerbated with repeated contact. If it contacts the eyes,

there may be corneal injury. Unfortunately, so me inst itut ions have used

glutaraldehyde inappropriately to disinfect f loors, walls, and l inen (96).

Ductless fume hoods are av ailable for glutaraldehyde (Fig. 34.6). A neutralizer

should be added to the solut ion when it is t ime for disposal. This wil l el iminate

P.970

the vapors that are c reated when disposing of the solut ion. In some localit ies, i t is

i l legal to put un-neutralized glutaraldehyde into the sewage s ystem.

Glutaraldehyde-neutralizing absorbent mats can be placed under and around baths

and washers to absorb and neutralize spil ls.

O r t h o p h t h a l a l d e h y d e

Orthophthalaldehyde (OPA or Cidex OPA) can achieve high-level disinfect ion at

room temperature after a 12-minute exposure and after a shorter t ime at an

elevated temperature (30,97 ,98 ,99). I t is sporicidal with prolonged exposure (10 0).

I t is often used in an automatic endoscope processing system, which reduces the

processing t ime to 5 minutes (30). I t is noncorrosive. Test str ips to measure the

minimum effect ive c oncentration are available and should be employed prior to

each use. Some localit ies require that OPA be neutralized before disposal.

Neutralizers that change color with deactivat ion are available.

OPA has a number of advantages compared with glutaraldehyde. These include

faster disinfection, minimal odor, no need for activation or mixing, and no OSHA

vapor l imit. I t c an be discarded through the drain. I t is effect ive in the presence of

organic soil. While signif icantly more expensive per gallon than glutaraldehyde, it

may be more economical at high-volume centers (10 1).

While side effects and hazards are l ess with OPA than with glutaraldehyde, eye

contact may cause st inging, excess tearing, and redness. I t stains proteins

(including unprotected skin), and repeated contact may cause dermatit is. Lesions of

the skin, l ips, mouth, and esophagus have been reported following prolonged use of


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a transesophageal echocardiograph probe that may have been improperly

processed with this agent (102 ).

Q u at er n ar y A mm o n i u m C om p o u n d s

Quaternary ammonium compounds (quats) are low-level disinfectants (5). They are

bactericidal, fungicidal, and v irucidal at room temperature within 10 minutes but

have not demonstrated sporicidal effects. I f a spore is coated with a quaternary

ammonium compound, it wil l not develop into a vegetat ive cell as long as the

germicide remains, but if the coating is removed, the spore can germinate. These

compounds are more effect ive against gram-posit ive than gram-negative bacteria.

Quats inactivate the human immunodeficiency v irus (HIV) but some do not

inactivate the hepatit is virus. They are ineffect ive against M. tuberculosis o rhydrophil ic viruses (2,87).

Early generation quats were affected by factors such as hard water, soap, anionic

residues, and proteinaceous soils. They were inactivated by organic materials (e.g.,

cork, cotton, and gauze pads). Some, either used in insuff icient concentrat ions or

in solut ions deteriorated by age or deactivated by the presence of organic soil , not

only fai led to k i l l some microbes but actually supported their growth (8). Newer

ones are mixed with various substances to p roduce synergist ic antimicrobial and

detergent activit ies while maintaining the hard water, protein, and anionic tolerance

necessary in environmental disinfectants. They are quick ac t ing, relat ively nontoxic,

and noncaustic and do not produce noxious fumes. They are useful for c leaning as

well as disinfect ion.

P h e n o l ic C om p o u n d s

Phenolic compounds (phenolics, phenols) are derived from carbolic acid (phenol),

one of the oldest germicides (2,5,8,87 ). They are sometimes combined with

detergents to form detergent germicides. They are good bactericides and a re act ive

against fungi. They are act ive in the presence of organic matter and soap. Phenols

are very s table and remain act ive after mild heating and prolonged drying. When

moisture is applied to a surface that has been previously treated with a phenolic

compound, it can redissolve the chemical so that it again becomes bactericidal.

Phenolics remain act ive in contact with organic soil and for this reason are often

the disinfectants of choice when dealing with gross organic contamination in

general housekeeping.

Most phenolics have a bad odor and are irr i tat ing to skin. They are absorbed by

rubber and may damage the skin or mucous membranes that they contact. They are


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diff icult to r inse from most materials, and residual disinfectant may cause t issue

irr itat ion or hyperbil irubinemia in neonates.

Phenols are considered i ntermediate- to low-level disinfectants. Most phenolic

detergents are tuberculocidal, fungicidal, and bactericidal when used as directed.

Certain viruses, including those associated with widespread common respiratory

il lnesses, are resistant to these compounds. The phenolics are not s poricidal

except at or above 100C. They are used mainly on environmental surfaces and for

noncrit ical devices.

A l c o h o l s

Within health care facil i t ies, alcohol usually refers to either ethyl or isopropyl

alcohol, both of which are water-soluble compounds that are intermediate- or low-level disinfectants (3). The alcohols are best us ed at concentrat ions of 70% to 90%

by volume. Both are effect ive against most viruses, including those for hepatit is B

(HBV) and AIDS (or HIV). The CDC recommends exposure to 70% ethanol for 15

minutes to inactivate HBV, but 1 minute should be adequate for HIV. Alcohols

display high ac t ivity against gram-negative bacteria, fungi, and M. tuberculosis but

cannot inactivate bacterial spores. Isopropyl alcohol cannot ki l l certain hydrophil ic

viruses.

Alcohols hav e a clea ns in g act ion , bu t wi ping a surface wi th an al coho l solu tion ma y

not maintain a 1-minute contact t ime between the surface to be disinfected and the

solut ion (11). They are inactivated by protein but not by soap. I t is not necessary to

rinse items soaked in alcohol, because it evaporates rapidly. For this reason, an

alcohol f lush cycle is used in some automatic processing

P.971

machines. The f lush cycle may be useful to disinfect the channels of f lexible f iber-

optic endoscopes. After high-level disinfection with a chemical germicide and a tap

water r inse, alcohol can remove minor water contaminants. I ts speed of evaporation

promotes rapid drying in the channels. Alcohols are often used to clean the external

surfaces of f iberoptic cables and scopes.

An important us e of a lc oho l is in ha nd rubs (103 ). These reduce the bacteria count

on hands more rapidly than antimicrobial soaps o r detergents. The Associat ion for

Professionals in Infection Control and Epidemiology (APIC) guidelines urge use of

an alcohol-based rub before and after patient contact and after any possible


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contact with body f luids and substances, mucous membranes, broken skin, or

contaminated objects.

Alcohol an d age nts con ta ining alcohol mus t not be a ll owed to ge t into an es thesia

gas sampling l ines, as this can lead to incorrect results when measuring anesthetic

agents (10 4). Alcohols can damage the lens mounts on instruments and tend to

swell and harden rubber and certain plast ics with repeated use (2). Alcohols are

flammable, so care must be taken not to use them in the presence of a heat source

that could ignite the vapor. Alcohol solut ions should be s tored in special f lammable-

materials cabinets (Fig. 34.12).

Io d i n e C omp o u n d s

An iodopho r is a combinati on of iodine and a sol ubil izing agent or carr ier wi th theresult ing complex providing a s ustained-release reservoir of iodine and releasing

free iodine in a queous solut ion (2,3,5,8). Iodophors are bactericidal, virucidal, and

tuberculocidal but may require prolonged contact t ime to ki l l certain fungi and

bacterial spores. Some iodophors do not ki l l M. tuberculosis ( 87 ).

Iodophors a re used principally as antiseptics but are capable of intermediate- and

low-level disinfect ion. Iodophors formulated as antiseptics are not suitable for

disinfect ing medical instruments or environmental surfaces ( 8). Some iodophors are

unstable in the presence of hard water, heat, and organic soil, but most are reliable

general-purpose disinfectants if used in concentrat ions recommended by the

manufacturer. Some metall ic instruments may become corroded if they are routinely

disinfected with iodophors; nonmetall ic items are seldom damaged but may be

stained or discolored.

Per a c et i c A c i d

Peracetic (peroxyacetic) acid is bac tericidal, fungicidal, virucidal, and sporicidal at

low temperatures (3 ,5 ,68 ,105,106,10 7,10 8,109 ,110 ). I t remains effect ive in the

presence of organic material. I t may be effect ive against prions (111). An important

advantage is that its decomposit ion products (acetic acid, water, oxygen, and

hydrogen peroxide) are not harmful. I t ca n corrode copper, brass, bronze, plain

steel, and galvanized iron, but these effects can be reduced by addit ives and pH

modif icat ions (88 ). A concentrated solut ion can cause eye and skin damage, but i t

has no OSHA exposure l imit.

Steris 20 is a patented product that has been developed specif ically for Steris

processors. The act ive ingredient is a concentrate of 35% peracetic acid plus

corrosion and degradation inhibitors that are contained in a sealed, single-use


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container. I t should be used only i n a Steris processing system. I t is not intended

for open-pan techniques.

A Ste ri s sys tem is sho wn in Figure 34.8. Equipment to be steri l ized must be c lean

but need not be dry. The equipment is placed in a special tray, which is then

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placed in the processor. The steri l izer has a variety of trays, containers, and

adaptors to accommodate various medical devices. Each tray has holes for f luid

entry and drainage and is designed so that there is a continuous f low of steri lant on

exposed surfaces and through internal channels of i nstruments.

View Figure

Figure 34.8The Steris system A:Items to be sterilized arecleaned, then placed in a tray. The tray is then placed in the

sterilizer. B:After the lid is closed and the processing cycleis started, the processor automatically opens the sterilant

concentrate and mixes it with filtered water. The usedilution of the sterilant enters the tray, covering the

instruments, and is circulated for 12 minutes. It is thendrained from the chamber, and the chamber and tray are

rinsed four times with sterile water. Next, sterile air ispumped into the chamber to displace the rinse water. A

printout is provided, confirming that the sterilizationparameters were met.


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View Figure

Figure 34.9The sealed package of sterilant is placed in theprocessor, and the lid is punctured before the lid is closed.

Af ter the tra y is pos iti on ed in the Ste ris proc essor, a seal ed package of s te ri la nt

concentrate is placed in the steri l izer (Fig. 34.9). The l id is closed and the

processing cycle started. During the cycle, the l id is sealed. The processor

automatically opens the steri lant concentrate and mixes it with a controlled volume

of filtered sterile water heated to between 50C and 56C. The diluted sterilant

enters the tray, covering the instruments, and is ci rculated for 12 minutes. I t is then

drained from the chamber, and the instruments and chamber are rinsed four times

with steri le water. Then, steri le air i s pumped into the chamber to displace the rinse

water. The cycle takes from 20 to 45 minutes, depending on the init ial temperature

of the water and how extensively the local water supply must be f i l tered. After the

cycle is complete, the unit f lushes the diluted steri lant and rinse water direct ly into

a drain. The tray can be transported direct ly to a s teri le f ield.

The Steris processor monitors and maintains the parameters necessary to ensure

steri le processing. I t wil l stop the cycle if a process error is detected. At the end of

each cycle, a p rintout confirming that the steri l izat ion parameters were met is

provided. Spore str ips can be used as biological monitors. These go through the

steri l izer and are then retrieved for culturing.

The Steris system provides a quick method of dis infect ing a wide variety of heat-

sensit ive immersible instruments, including f iberscopes (112,11 3) (Fig. 34.10). The

Steris system has been found to be effect ive in s teri l izing the lumens of

endoscopes when organic soil and salt were present (114).


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View Figure

Figure 34.10Endoscope in Steris processor. Note thetubings that are connected to the channels.

The Steris system is less damaging to delicate instruments than steam steri l izat ion

and is compatible with a wide variety of materials, including plast ics, rubber, and

most heat-sensitive items. It is important that the absence of long-term effects on

the devices being steri l ized by the Steris system are confirmed with the instrument

manufacturer. Polymers, glasses, coatings, adhesives, and sealants that are

typically used in medical devices are compatible with the p rocess. Untreated metals

such as copper, brass, si lver, aluminum, and iron are subject to oxidation.

Alum inum anod ize d coa t ing can bec ome du ll .

The Steris system is especially useful f or items requiring a quick turnaround t ime. I t

is faster than s teri l izat ion with EO or glutaraldehyde and can be used on wet or dry

items. No steri lant dilut ion is necessary, and personnel are not exposed to a ny

toxic chemicals. Consequently, i t can be located in the operating room suite. The

site requirements are a tap water supply, a drain, and electricity. I t l eaves no

residue. Wrapping is not necessary.

This system does have s ome disadvantages. Unlike some automated processors,

the Steris machine has no cleaning cycle. Costs per cycle are greater than if

glutaraldehyde is used (11 5). Only i tems that c an be totally immersed can be

steri l ized, and only a small number of instruments can be processed in a cycle. The

trays cannot be used for extended storage, so processing must be consistent with

just-in-t ime delivery.

Ch l o r i n e C omp o u n d s


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Several chlorine compounds are available for use as disinfectants, including

sodium and calcium hypochlorite (household bleach), chlorine dioxide, and

chloramine T (3,5,11 6). The hypochlorites are

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the most widely used. They are inexpensive and fast act ing. They are available in

both l iquid (sodium hypochlorite) and solid (calcium hypochlorite) form. Relat ively

low concentrat ions of sodium hypochlorite (50 ppm) exhibit rapid act ivity against

vegetat ive bacteria. One hundred ppm is effect ive against most fungi. Many vi ruses

are inactivated at concentrat ions of 200 ppm, with HIV being susceptible at

concentrat ions as low as 50 ppm. HBV exhibits marked inactivat ion at 500 ppm.

Concentrat ions of 1,000 ppm are considered adequate to achieve high-level

disinfect ion. A 1:5 to 1:10 di lut ion wil l destroy the agent of Creutzfeldt-Jakob

disease (CJD) after an exposure time of 1 hour (11 7).

TABLE 34.2 Preparation of Household Bleach for Disinfectionaa

Desir ed Chlor ine Concentration 5,000 ppm1,000 ppm 500 ppm 100 ppm

Dilution for use within 24 hours 1:10 1:50 1:100 1:500

Dilution for use for 1 to 30 days 1:5 1:25 1:50 1:250

aStarting with 5.25% NaOCl, which contains 50,000 ppm of free chlorine.

Table 34.2shows the dilut ion of 5.25% NaOCl (household bleach) needed to

achieve the desired chlorine concentrat ion. Solut ions that wil l b e used for extended

periods (1 to 30 days) should have an init ial concentrat ion twice as high as actually

desired and should be stored in an opaque container.

Chlorine solut ions are not often used for instrument disinfect ion but have been

used widely in environmental disinfection. Current OSHA regulations consider

dilut ions of 1:10 to 1:100 chlorine to be acceptable for use with b lood spil ls. Other


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uses include spot disinfect ion of countertops and f loors and decontamination of

resuscitat ion manikins.

Highchlorine compound concentrat ions are corrosive as well as irr i tat ing to

personnel, and their use should be l imited to si tuat ions in which there are unusually

high concentrat ions of microorganisms (8). Their use is l imited by their

corrosiveness, inact ivat ion by organic matter, and relat ive instabil i ty. They may

leave a residue and are irr i tat ing to the skin, eyes, and respiratory tract.

Chlorine dioxide is used in a gaseous phase (11 8). I t is not stored but is generated

at the point of use. Advantages are that it leaves l i t t le residue and is nonozone

deplet ing. Disadvantages involve material incompatibil i ty.

Hy d r o g e n P er o x i d eHydrogen peroxide is an effect ive bactericide, fungicide, virucide, and s poricide

(2,3 ,5,11 9,120). I t is commercially available in sev eral dif ferent concentrat ions. I t is

not inact ivated by organic matter. There are no restrict ions on disposal. I t rapidly

loses effect iveness when exposed to heat and l ight and requires careful s torage. I t

can damage rubber and plast ic and may corrode copper, zinc, and brass. I t is an

irr itant to the skin and eyes. A 7.5% solut ion achieves high-level disinfect ion in 30

minutes. An effect ive low-level disinfectant, 3% hydrogen peroxide is useful for

work surfaces. Hydrogen peroxide is used for plasma sterilization (see below).

Ozo n e

Ozone steri l izers use oxygen, water, and electricity to produce ozone

(121 ,122,123). The gas is humidif ied and dispersed into a steri l izat ion chamber. A

steri l izat ion cycle includes three stages: air evacuation, fol lowed by air and ozone

mixture admission; an exposure stage; and a stage of v acuum-drying and ozone

removal. After the cycle, the ozone passes through a catalyt ic converter that

changes it back to ox ygen.

Ozone steri l izat ion is good for most goods that need low-temperature steri l izat ion.

It is not approved for f lexible scopes and reactive metals such as copper and brass.

It is compatible with most anodized aluminum steri l izat ion containers and all plast ic

containers. I t is unsuitable for devices that contain natural gum rubber products,

some plast ics, and some metals such as brass and copper.

Accordin g to the ma nu fac tu rer, ozo ne can steri l ize s in gle s tai nl es s s te el lumens

with an inside diameter of 2 mm and no longer than 250 mm, lumens with an inside

diameter of 3 mm or larger and no longer than 470 mm, and those with an inside

diameter of 4 mm and no longer than 600 mm (121,122 ).


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The process is environmentally fr iendly and produces no toxic residuals. I t requires

no vent or drain and uses only oxygen, electricity, and a l i t t le water. The steri l izer

can be transported easily. No exhaust gas venti lat ion duct is required in a room

that is adequately venti lated. The treated objects are dry. No rinsing or degassing

is required. While signif icantly slower than gas plasma, this process is less

expensive.

F o rma l d e h y d e

Formaldehyde is a highly toxic and f lammable gas that has been used as a

disinfectant and a steri lant in both a water-based solut ion (formalin) and the

gaseous state (5). I t is noncorrosive and is not inact ivated by organic matter.

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Al though formali n is a high -lev el dis in fe cta nt , i ts uses are l im ite d by its pu ng en t

odor and fumes, which irr i tate the skin, eyes, and respiratory tract. I ts toxicity

requires that disinfected materials be thoroughly rinsed before use. NIOSH has

indicated that formaldehyde should be handled as a potent sensit izer and probable

carcinogen. Kits are available to absorb and neutralize formaldehyde spil ls.

Steri l izat ion with low-temperature steam and formaldehyde is used in some

countries (5 ,124).

Advantages and Disadvantages of Chemical Disinfection

and Sterilization

Adv an ta ges of l iquid chem ic al disinf ec ti on inc lu de econom y, speed, and simpl ic ity.

This is es pecially important in busy endoscopy suites because it enables equipment

to be used several t imes a day. I t is useful for equipment that does not require

steri l izat ion but does require high-level disinfect ion.

Chemical disinfect ion cannot be used for all types of equipment. Many devicescannot be soaked. Prepackaging is not possible, and the equipment wil l be wet.

There is a r isk of recontamination during subsequent r insing, drying, or wrapping.

With most agents, steri l i ty cannot be guaranteed. I t is more expensive, less

effective, and more prone to human error than steam sterilization. Hinged

instruments must be opened and those with sl iding or mult iple parts disassembled.

Some solut ions are irr i tat ing to t issues and have unpleasant odors. Personnel who

handle them must take precautions to avoid prolonged skin contact or vapor


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inhalat ion (92 ). The chemicals may be absorbed onto the treated items, causing

harm to the patient.

A sign if icant di sadvan tage of cold s te ri l izati on is the lack of a good method for

validat ion. The eff icacy can be monitored only indirect ly, through surveying patient

outcomes, to identify s ubsequent infect ions that can be attr ibuted to exposure to

the reusable device (125 ). Most health care inst itut ions have an act ive surveil lance

program in which infect ion control pract it ioners seek to identify nosocomial

infect ions.

Gas St e r i l i z a t i o n

Characteristics of Ethylene Oxide

Ethylene oxide (EtO, EO) is a colorless, poisonous gas with a sweet odor

(126 ,127,128,129 ,130,13 1,132 ,133 ,134). I t is available in high-pressure tanks and

unit-dose ampules and cartr idges. I t is f lammable in concentrat ions of 3% or

greater. Manufacturers have dealt with this hazard in two ways. EO may be mixed

with carbon dioxide or hydrochlorof luorocarbons (HCFs). Mixtures containing up to

12% EO in these inert di luents are nonflammable but retain their steri l izing abil i ty.

A mix ture of EO and chlo ro f lu oro carbo n (CFC ) was us ed in the pas t, but the us e of

CFCs was banned because of damage to the ozone layer. HCFs are s imilar to CFCs

but are less damaging to the ozone layer (127,13 5). Their use wil l be eliminated in

the United States by 2030.

EO is supplied mostly as 100% in small c ylinders, cartr idges (Fig. 34.11), or

ampules. Equipment is designed for gas containment and to minimize the risk of

f ire or explosion (12 6,127,13 6). A cartr idge is punctured only after it is secured in a

sealed and locked steri l izat ion chamber. An ampule is broken only after it is placed

in a bag with the medical device to be steri l ized. Explosion-proof cabinets should

be used for storing cartr idges of 100% EO (Fig. 34.12).

EO kil ls bacteria, spores, fungi, and v iruses. I t penetrates into crevices and through

permeable bags. I t is not degraded by organic soil but wil l not penetrate dried

protein material.

Preparation for Ethylene Oxide Sterilization

I t is important to verify that a device is suitable for steri l izat ion using EO. The

manufacturer's instruct ions should be c onsulted. Some devices need to be

steri l ized at a lower temperature.


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Before packaging, items must b e disassembled, cleaned, dried, and wrapped.

Disassembly is important to remove barriers to free movement of gas. Caps, plugs,

valves, and/or stylets must be removed. Hollow-bore

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products such as needles and tubes must be open at both ends. The wrapping must

be permeable to EO gas and water vapor and allow proper aeration ( 13 7).

View Figure

Figure 34.11Cartridge of EO. The cartridge is puncturedonly after the sterilizer door is closed and locked and properconditions are met. There are no external tanks, hoses, or

gas source hookups, which are major sources of potentialoperator exposure to EO.

View Figure

Figure 34.12Explosion-proof cabinet for flammablematerials.

Blood and other proteinaceous materials can act as a barrier to EO. I f salt and

protein are present in a narrow lumen, steri l izat ion wil l not be achieved consistently


39/126

(114 ). Therefore, equipment must be thoroughly cleansed and rinsed before

steri l izat ion.

Items for gas steri l izat ion must be free of water droplets. They should be allowed to

dry in ambient air or towel dried. The use of h eated air should be avoided because

EO steri l izat ion depends on the presence of adequate (but not excessive) moisture.

A re lat ive humidity between 35% and 70% an d a te mpera ture be tween 18C and

22C throughout the processing and s torage facil i ty are recommended (23 ,128).

Devices should be s orted according to the steri l izat ion t ime and recommended

temperature. I tems to b e steri l ized are placed in wire baskets, metal steri l izer carts,

or other carriers that do not absorb EO. The steri l izer manufacturer's instruct ions

for loading should be carefully fol lowed. I tems should be loaded loosely to allow

gas to penetrate throughout the load. I tems should be loaded in such a fashion that

packages will not contact the chamber walls or the operator's hands when the load

is transferred to the aerator. Some instruments are steri l ized in r igid containers that

have f i l ters on the l id and bottom to allow dif fusion of steri lant gas. There may also

be an addit ional l id attached to the upper l id.

The Sterilization Process

P r o c e s s i n g P a r am e t er s a f f e c t i n g E t h y l e n e O x i d e

S t e r i l i z a t i o n

Gas Concentration

As th e EO concentr at io n inc reases at a g iv en temp era tu re an d rel ati ve hu mi di ty,

the microbial inact ivat ion rate increases up to a certain range when it begins to

plateau (12 6). EO concentrat ions between 450 and 750 mg/L are commonly used in

processing medical products. The solubil i ty of EO in the product and the dif fusion

rate through the product wil l inf luence the steri lant concentrat ion. The operating

pressure of the EO cycle wil l greatly inf luence the gas dif fusion rate. Packaging

may also be cri t ical. Devices that perform continuous EO monitoring in the

steri l izat ion chamber are av ailable.

Temperature

Increasing the temperature can decrease the necessary exposure time. Many

steri l izers provide a select ion of temperatures. In health care, processing cycles

are commonly performed between 38C and 60C. Some conduct sterilization at

room temperature. This is equally eff icacious if other factors (exposure t ime and

concentrat ion) are adjusted.


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Relative Humidity

Moisture hydrates microbes, making them more susceptible to destruct ion by EO.

Therefore, humidity must be controlled in the storage and cleaning/processing area

and in the steri l izer itself . Most EO chambers are held between 40% and 80%

relat ive humidity. Desired humidity levels are usually accomplished by low-

temperature steam inject ion. For tabletop monitors, i t is necessary to add water to

the steri l izer.

Exposure Time

The necessary steri l izat ion t ime wil l depend on the factors mentioned previously.

The t ime generally ranges between 1.5 and 6 hours in automatic steri l izers. Up to

12 hours may be required.

S t e r i l i z e r s

EO steri l izers range in s ize from small tabletop to large f loor-loading models (126 ).

The basic design includes a p ressure-rated vessel with a p ort for admitt ing air, a

vacuum pump to evacuate the chamber gas contents, a jacket to heat the vessel, a

steam source to humidify the chamber and its contents, and a means to inject the

sterilant. A recent change has been to integrate computers, microprocessors, and

software into the control, monitoring, and documentation of s teri l izat ion processing.

Anc il lary equipm en t such as recirc ul ati on blowe rs to equ il ibrate the chamber

environment, exhaust systems to minimize release of steri lant into the work

environment on door opening, an

chapter 34. cleaning & sterilization

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