ASTM F3537-21

Standard Guide for Respirator Fit Testing Methods

SIGNIFICANCE AND USE
4.1 The purpose of this guide is to provide clear and consistent guidance with regard to the respirator fit-testing components of an effective respiratory protection program.  
4.2 The respirator fit test itself is simply one facet of fit testing. An effective program requires much more, including a qualified person to perform the fit test. This guide provides guidance on exactly what knowledge and skills are necessary to perform as a qualified fit test operator.  
4.3 This guide contains information to aid program managers and fit test operators in preparing to perform a proper fit test. This includes guidance regarding potential interference from other personal protective equipment (PPE) with the respirator, detailed information on respirators used for fit testing, selection of respirators before fit testing, and other considerations that shall be met if the fit test is to be effective.  
4.4 A single fit test exercise protocol cannot model all workplace activities encountered by respirator users. Recognizing this, this guide provides flexibility regarding fit test exercise protocols. Exercises may be selected that are more representative of actual workplace activities, including repeated respirator donning.  
4.5 Exceptions—Users of this guide should be aware that regulatory agencies may have requirements that are different from this guide.
SCOPE
1.1 This guide provides guidance on how to conduct fit testing of tight-fitting respirators and appropriate methods to be used. Fit testing is only one element of a complete respiratory protection program. Examples of complete respiratory protection programs are defined in Practice F3387, 29 CFR 1910.134, and so forth.  
1.2 Purpose—This guide provides requirements for conducting respirator fit testing and includes:  
1.2.1 Qualifications for fit test operators,  
1.2.2 Specific fit test methods,  
1.2.3 Interpretation of fit test results,  
1.2.4 Recordkeeping, and  
1.2.5 Methods to validate new fit test methods.  
1.3 Should and Shall—The provisions of this guide are mandatory in nature when the word “shall” is used and advisory in nature when the word “should” is used.  
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

General Information

• Status: Published
• Publication Date: 31-Oct-2021
• ICS: 13.340.30 - Respiratory protective devices
• Technical Committee: F23 - Personal Protective Clothing and Equipment
• Drafting Committee: F23.65 - Respiratory

Relations

• Refers: ASTM F3387-23 - Standard Practice for Respiratory Protection
• Effective Date: 01-Nov-2023
• Refers: ASTM F3387-19 - Standard Practice for Respiratory Protection
• Effective Date: 01-Aug-2019

Overview

ASTM F3537-21: Standard Guide for Respirator Fit Testing Methods provides clear and consistent guidance for conducting fit testing of tight-fitting respirators. Developed by ASTM International, this standard outlines procedures necessary to verify that a selected respirator fits the wearer, helping ensure the effectiveness of respiratory protection programs. The guide also clarifies essential knowledge and skills required for fit test operators and offers flexibility in fit test exercise protocols to best reflect real-world workplace scenarios. Compliance with this guidance helps organizations fulfill health and safety requirements and improves workplace safety culture.

Key Topics

• Fit Testing as Part of Respiratory Protection Programs

  • Fit testing is a critical component but only one element of a complete respiratory protection program. Programs should reference other standards such as ASTM F3387 and 29 CFR 1910.134.

• Qualifications for Fit Test Operators

  • Operators must be properly trained, demonstrate proficiency in fit testing methods, and be familiar with relevant aspects of respiratory protection.
  • Continual training and assessment are recommended.

• Fit Test Methods

  • Both qualitative (QLFT) and quantitative (QNFT) fit test methods are addressed.
  • Methods include guidance for selection, preparation of respirators, and interpretation of results.

• Interpretation of Fit Test Results & Recordkeeping

  • The guide defines how to interpret fit test outcomes and specifies the need for thorough recordkeeping.

• Parameters for Effective Fit Testing

  • Addresses factors such as interference from other personal protective equipment (PPE), proper selection and preparation of respirators, and identification of potential issues such as facial hair or incorrect donning.

• Regulatory Alignment

  • Recognizes that certain regulatory agencies may have requirements that differ from this guide, and users need to verify the applicable standards.

Applications

ASTM F3537-21 is essential for:

• Health and Safety Managers seeking to develop or enhance workplace respiratory protection programs in compliance with OSHA (29 CFR 1910.134) or other applicable standards.
• Fit Test Operators and Program Administrators needing detailed requirements and best practices for conducting proper respirator fit tests, including the correct use and maintenance of fit testing equipment.
• Industrial Settings where employees may be exposed to hazardous airborne contaminants and must use tight-fitting respirators, such as manufacturing, healthcare, construction, laboratories, and emergency response teams.
• Training Providers and Safety Consultants providing fit testing training or service to third-party organizations.

Using ASTM F3537-21 supports:

• Consistent execution of respirator fit tests.
• Improved worker protection against hazardous atmospheres.
• Enhanced compliance with relevant U.S. regulations and international best practices.

Related Standards

Understanding fit testing in the broader context requires familiarity with related standards and regulations:

• ASTM F3387 – Practice for Respiratory Protection: Offers a comprehensive framework for overall respiratory protection programs.
• ANSI/ASSE Z88.2 – Practices for Respiratory Protection: Addresses program management and selection of respiratory protective devices.
• ANSI/AIHA Z88.6 – Respirator Use-Physical Qualifications for Personnel: Discusses health assessments for respirator users.
• 29 CFR Part 1910.134 – OSHA standard for respiratory protection programs.
• World Trade Organization TBT Committee Principles – Ensures development of international standards and guides.

By following ASTM F3537-21 and associated standards, organizations demonstrate a commitment to occupational health and safety, regulatory compliance, and global best practices in respiratory protection and fit testing.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: F3537 − 21
Standard Guide for
Respirator Fit Testing Methods
This standard is issued under the fixed designation F3537; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 ANSI Standards:
ANSI/ASSE Z88.2Practices for Respiratory Protection
1.1 This guide provides guidance on how to conduct fit
ANSI/AIHA Z88.6 Respiratory Protection—Respirator
testingoftight-fittingrespiratorsandappropriatemethodstobe
Use—Physical Qualifications for Personnel
used. Fit testing is only one element of a complete respiratory
protection program. Examples of complete respiratory protec- 2.3 Federal Standard:
29 CFR Part 1910.134Respiratory Protection
tionprogramsaredefinedinPracticeF3387,29CFR1910.134,
and so forth.
3. Terminology
1.2 Purpose—This guide provides requirements for con-
ducting respirator fit testing and includes: 3.1 Definitions:
3.1.1 aerodynamic diameter, n—diameter of a unit density
1.2.1 Qualifications for fit test operators,
1.2.2 Specific fit test methods, sphere having the same settling velocity as the particle in
1.2.3 Interpretation of fit test results, question.
1.2.4 Recordkeeping, and
3.1.2 aerosol, n—particles, solid or liquid, suspended in air.
1.2.5 Methods to validate new fit test methods.
3.1.3 canister/cartridge, n—container with a filter, sorbent,
1.3 Should and Shall—The provisions of this guide are
catalyst, or combination of these items that removes specific
mandatory in nature when the word “shall” is used and
contaminants from the air passed through the container.
advisory in nature when the word “should” is used.
3.1.4 challenge agent, n—aerosol, vapor, or gas used by the
1.4 Units—The values stated in SI units are to be regarded
fit test method for detecting respirator leakage.
asstandard.Nootherunitsofmeasurementareincludedinthis
3.1.5 challenge pressure, n—negative static pressure estab-
standard.
lished inside the respirator facepiece during a controlled
1.5 This standard does not purport to address all of the
negative-pressure fit test.
safety concerns, if any, associated with its use. It is the
3.1.6 facepiece, n—see tight-fitting respirator.
responsibility of the user of this standard to establish appro-
3.1.7 filter, n—component used in respirators to remove
priate safety, health, and environmental practices and deter-
aerosols from the inspired air.
mine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accor- 3.1.8 fit factor, n—numeric expression of how well a tight-
dance with internationally recognized principles on standard-
fitting respirator fits a wearer during a quantitative fit test.
ization established in the Decision on Principles for the 3.1.8.1 Discussion—Itistheratioofthemeasuredchallenge
Development of International Standards, Guides and Recom-
agent concentration outside the respirator (C ) to its concen-
out
mendations issued by the World Trade Organization Technical tration inside the respirator (C ). (Fit factor = C / C ).
in out in
Barriers to Trade (TBT) Committee.
3.1.9 fit test, n—use of a qualitative or quantitative protocol
to evaluate sealing surface leakage of a specific tight-fitting
2. Referenced Documents
respirator while worn by an individual.
2.1 ASTM Standards:
3.1.10 fit test method, n—combination of instrumentation,
F3387Practice for Respiratory Protection
technology, and protocols used to conduct a respirator fit test.
1 3.1.10.1 Discussion—An accepted method may have more
This guide is under the jurisdiction of ASTM Committee F23 on Personal
ProtectiveClothingandEquipmentandisthedirectresponsibilityofSubcommittee
than one accepted protocol.
F23.65 on Respiratory.
Current edition approved Nov. 1, 2021. Published November 2021. DOI:
10.1520/F3537-21.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM 4th Floor, New York, NY 10036, http://www.ansi.org.
Standards volume information, refer to the standard’s Document Summary page on Available from U.S. Government Publishing Office (GPO), 732 N. Capitol St.,
the ASTM website. NW, Washington, DC 20401, http://www.gpo.gov.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F3537 − 21
3.1.11 fit test operator, n—person qualified by training and 4.5 Exceptions—Users of this guide should be aware that
experience with demonstrated ability to perform properly regulatory agencies may have requirements that are different
qualitative or quantitative fit tests and evaluate test results. from this guide.
3.1.12 fit test protocol, n—specific step-by-step instructions
5. Fit-Testing Rationale
for conducting a respirator fit test.
5.1 The purpose of respirator fit testing is to verify that the
3.1.13 penetration, n—numerical expression of how well a
selected make, model, and size of a tight-fitting respirator
tight-fittingrespiratorfitsawearerduringaquantitativefittest.
adequately fits the wearer. This is accomplished so there is
3.1.13.1 Discussion—For aerosol-based quantitative fit test
reasonable assurance that the wearer has learned to don the
methods, it is the ratio of the measured challenge agent
respirator properly and can achieve the anticipated protection
concentration inside the respirator (C ) to its concentration
in
during use. Fit testing is a critical component of a respirator
outside the respirator (C ). (Penetration = C / C ).
out in out
training program.
3.1.14 qualitative fit test, QLFT, n—pass/failfittestincluded
in this guide that relies on the subject’s sensory response to 6. Qualifications for Fit Test Operators
detect a challenge agent.
6.1 General Qualifications:
3.1.15 quantitative fit test QNFT, n—fit test included in this
6.1.1 Fit test operators shall be properly trained and dem-
guide that uses an instrument to measure face seal leakage. onstrate a proficiency in the fit test method(s) being used. The
respiratory protection program administrator is responsible for
3.1.16 required fit factor, RFF, n—numericvalueestablished
evaluating and verifying the training and qualification of
as a pass/fail point or acceptance criterion for a quantitative fit
operators.
test.
6.1.2 Program administrators may wish to consider the
3.1.17 respirator, n—personal protective device designed to
benefitsofformaltrainingprogramsfromoutsideprovidersfor
protect the wearer from the inhalation of hazardous atmo-
fit test operators.An evaluation form for fit test operators is in
spheres.
Annex A2. Continue training fit test operators until all ques-
tionsontheformcanbemarked“acceptable”bytheevaluator.
3.1.18 tight-fitting respirator, n—respiratorwithafacepiece,
Determination of acceptability for each item is left to the
hood, or helmet that is designed to form a complete seal with
discretion of the respiratory protection program administrator.
the face or neck.
3.1.18.1 Discussion—This includes a hood or helmet with a 6.2 Specific Qualifications for Fit Test Operators:
neck seal (neck dam). 6.2.1 They shall be familiar with this guide along with the
appropriate sections of the respiratory protection program
3.1.19 user seal check, n—procedure conducted by the
concerning respirator fit testing, inspection, cleaning,
wearer to determine if a tight-fitting respirator is properly
maintenance, and storage.
donned.
6.2.2 They shall demonstrate a general knowledge of respi-
rators used by the wearer in the workplace by:
4. Significance and Use
6.2.2.1 Identifying respirator components and their func-
4.1 The purpose of this guide is to provide clear and
tions;
consistent guidance with regard to the respirator fit-testing
6.2.2.2 Demonstrating respirator inspection, cleaning, and
components of an effective respiratory protection program.
maintenance procedures;
6.2.2.3 Identifying different make, model, style, and size
4.2 The respirator fit test itself is simply one facet of fit
respirators;
testing.An effective program requires much more, including a
6.2.2.4 Discussing respirator capabilities and limitations as
qualified person to perform the fit test. This guide provides
related to respirator fit testing; and
guidance on exactly what knowledge and skills are necessary
6.2.2.5 Demonstrating and evaluating proper donning and
to perform as a qualified fit test operator.
doffing procedures, including user seal checks.
4.3 This guide contains information to aid program manag-
6.2.3 They shall demonstrate knowledge and application of
ers and fit test operators in preparing to perform a proper fit
the fit test method(s) being used by:
test. This includes guidance regarding potential interference
6.2.3.1 Explaining the purpose of respirator fit testing;
from other personal protective equipment (PPE) with the
6.2.3.2 Explaining fit test procedures;
respirator, detailed information on respirators used for fit
6.2.3.3 Explaining the limitations of the fit test method;
testing, selection of respirators before fit testing, and other
6.2.3.4 Identifying indications of erroneous fit test results
considerations that shall be met if the fit test is to be effective.
(for example, quantitative fit factors that are unusually low or
high); and
4.4 A single fit test exercise protocol cannot model all
workplace activities encountered by respirator users. Recog- 6.2.3.5 Demonstrating knowledge of the health and safety
hazards associated with the chemicals or equipment, or both,
nizing this, this guide provides flexibility regarding fit test
exercise protocols. Exercises may be selected that are more used in the fit test.
representative of actual workplace activities, including re- 6.2.4 They shall demonstrate the ability to set up all
peated respirator donning. applicable equipment for the fit test method(s) being used by:
F3537 − 21
6.2.4.1 Selectingthepropercanisters/cartridgesorfiltersfor 7.3.1 Facial Hair—Skin contacting respirator facepiece
the fit test method; sealing surfaces shall have been clean shaved within 24h of
testing, preferably within 12h.Aperson shall not be fit tested
6.2.4.2 Preparing, inspecting, and performing operational
checks of fit-testing equipment and materials; and if:
6.2.4.3 Proper assembly and use of probes and adapters for
7.3.1.1 Hair comes between the sealing surface of the
quantitative fit test methods.
respirator and the face or neck, and
6.2.5 They shall demonstrate the ability to conduct the
7.3.1.2 Hair interferes with valve or respirator function or
respirator fit test(s) being used by:
both.
6.2.5.1 Properly evaluating persons being fit tested and
7.3.2 Foreign Material—Afit test shall not be conducted if
understanding when to refuse to conduct a fit test by recogniz-
there is any foreign material or substance between the sealing
ing facial characteristics, facial hair, or other problems that
surfaceoftherespiratorandthefaceorneck.Examplesinclude
may interfere with respirator fit or the test;
temple bars or straps for eyewear, gels, creams, and so forth.
6.2.5.2 Explaining the fit test purpose and procedures to
7.3.3 PPE and Other Items That May Interfere with Fit—
persons being fit tested;
WhenanyPPEorrespiratoraccessoryorbothhasthepotential
6.2.5.3 Observingthatthecorrectdonningprocedureisused
to interfere with the seal, it shall be worn during the fit test to
without physically assisting the person being fit tested;
ascertain compatibility with the respirator. For example,
6.2.5.4 Observing that user seal checks are performed ac-
eyeglasses, goggles, face shield, head protection, skull cap,
cording to the procedures recommended by the respirator
hearingprotection,weldinghelmet,orotherprotectivedevices
manufacturer;
can potentially interfere with the seal of the respirator. This
6.2.5.5 Observing the person being fit tested throughout the
appliestoalltight-fittingrespirators,includinghalffacepieces.
entire fit test procedure to ensure the fit test is performed
7.3.4 Other Conditions That May Adversely Affect Fit—The
correctly;
fit test should be conducted with the respirator worn in the
6.2.5.6 Conducting the chosen test method according to the
manner in which it is used.
procedures specified in Sections 8 and 9;
7.3.4.1 Not every individual may be able to obtain a
6.2.5.7 Evaluating and recording the results of the fit test;
satisfactory fit. For example, certain facial characteristics may
and
interfere with respirator fit, such as: hollow temples, exces-
6.2.5.8 Performing respirator cleaning and sanitizing ac-
sivelyprotrudingcheekbones,deepskincreases,theabsenceof
cording to manufacturer instructions.
teeth or dentures, injury to the face, and swelling of the mouth
6.2.6 Theyshalldemonstratetheabilitytoidentifycausesof
or face.
fit test failure such as:
7.3.4.2 Respirator wearers who have dentures shall be fit
6.2.6.1 Improperly donned or adjusted respirator;
tested:
6.2.6.2 Incorrectly assembled or damaged respirator; and
(1)With dentures if they wear them while wearing the
6.2.6.3 Incorrect size, shape, or style respirator.
respirator in the workplace, or
(2)Without dentures if they do not wear them while
7. General Considerations
wearing the respirator in the workplace.
7.1 Medical Evaluation—Persons being fit tested shall be 7.3.4.3 Other factors may alter the seal of a respirator.
medicallyclearedtoweartherespiratorbeforefittesting.Refer Examples include cosmetics, facial jewelry, and certain hair
to ANSI/AIHA Z88.6, 29 CFR 1910.134, or other applicable styles.
regulatory standards.
7.4 Frequency of Fit Tests:
7.2 Training for Respirator Wearers:
7.4.1 Individuals wearing a tight-fitting respirator shall be
7.2.1 Personstobefittestedshallreceivetrainingbeforethe
fittestedbeforeinitialuseoftherespiratorwheneveradifferent
fit test.Amirror may be helpful to assist with positioning and
respirator (size, style, model, or make) is used and at least
adjusting the respirator. They shall be informed of the identity
annually thereafter.
of the challenge agent and any potential health and safety
7.4.1.1 One purpose of the annual fit test is to verify and
hazards of challenge agents used. They shall be able to:
refresh user training.
7.2.1.1 Properly inspect the respirator and recognize condi-
7.4.2 A fit test shall also be repeated when a person has a
tions that may compromise its integrity, such as missing
condition that may interfere with the respirator seal, such as:
components or deformities;
7.4.2.1 A significant change in weight,
7.2.1.2 Properly don the respirator without assistance; and
7.4.2.2 Achangetothefaceinthesealingarea(forexample,
7.2.1.3 Perform a user seal check.
scarring, facial surgery),
7.2.2 Instruction in proper donning may occur immediately
7.4.2.3 Dental changes, or
before the fit test or earlier and may involve assistance. After
7.4.2.4 User discomfort.
training, the fit test shall be conducted only after the respirator
is donned without any physical or verbal assistance. If assis-
7.5 Respirators Used for Fit Testing:
tance is provided, the person being fit tested shall completely
7.5.1 Fit testing of tight-fitting respirators shall be done
remove the respirator and don it again.
using either:
7.3 Interference Concerns: 7.5.1.1 The wearer’s individually assigned respirator, or
F3537 − 21
7.5.1.2 A surrogate respirator facepiece having sealing sample is drawn at a point midway between the nose and
surfaces, materials, and head straps that are the same as the mouth. The sample probe location shall follow the recommen-
respirator to be assigned to the wearer.
dations of the fit test equipment manufacturer. The sample
7.5.2 Respirators used for fit testing shall be equipped with probe should extend into the respirator cavity but not close
filtration or sorbent media or adapters, or both, appropriate for
enough to be blocked by the face. The in-facepiece sampling
the selected fit test method. The filtration or sorbent medium
pointshallnotbeisolatedfromthenoseormouthbyaphysical
used for fit testing may be different than those used in the
partition.Forexample,ifanosecupisusedonafullfacepiece,
workplace. The weight of cartridges, filters, and/or fit test
the sample point shall be inside the nose cup.
adapters used for fit testing can affect fit. Where possible, the
7.5.9 Maintenance of Equipment and Respirators Used for
respirator assembly used during the fit test should be represen-
Fit Testing—Fit-testingequipmentsuchasadapters,hoods,and
tativeoftherespiratorusedintheworkplace.Forexample,the
tubingshallbekeptinacleanandsanitaryconditionconsistent
weight of combination chemical/particulate cartridges may be
with manufacturer recommendations. Respirators used for fit
significantly higher than a particulate filter alone.
testingshallbeproperlyinspectedandmaintainedaccordingto
7.5.3 Tight-fitting positive-pressure respirators shall be fit
the respirator manufacturer’s recommendations.
tested only in the negative-pressure mode regardless of the
7.5.9.1 Respirators shall be cleaned and sanitized before
mode of operation used for respiratory protection. This is
being donned by different individuals. See the respirator
accomplished by either:
manufacturer’sinstructionsforrecommendedpractices.Surro-
7.5.3.1 Following the manufacturer’s instructions for tem-
gate respirator facepieces that cannot be sanitized (for
porarily converting the wearer’s individually assigned respira-
example, filtering facepieces) shall not be used by more than
tor into a negative-pressure respirator with appropriate filters,
cartridges, and/or adapters, or one individual.
7.5.3.2 Using a surrogate negative-pressure respirator face-
7.6 Choosing the Respirator—No one size or model of
piece with sealing surfaces and materials that are the same as
respirator can be expected to fit all faces. Different sizes and
the respirator to be assigned to the wearer. For example, a
models will accommodate more individuals. Therefore, an
negative-pressure air-purifying facepiece may be used as a
appropriate number of sizes and models shall be made avail-
surrogate facepiece for a powered air-purifying or SCBA
able from which a satisfactory respirator may be selected. The
facepiece made by the same manufacturer if the sealing
actualnumberofmodelsandsizesnecessarytofulfilltheintent
surfaces and materials are identical.
ofthisrequirementwillvarybyworkplace.Factorsthatshould
7.5.4 When fit testing tight-fitting hoods, the requirements
be considered in determining the number of respirators to be
for full facepiece respirators shall be used.
madeavailableincludethenumberofemployeesandemployee
7.5.5 Respirator modifications made to accommodate fit
acceptance factors.
testing shall not significantly alter the fit of the respirator.
7.6.1 Fittestoperatorsshallnotforce-fittherespiratorbeing
7.5.6 Respirators Used for QLFT—Respirators used for
fit tested. Force-fitting is the practice of repeating a failed fit
QLFT do not require modifications beyond those discussed
test with the same respirator by re-donning or otherwise
before. (In-facepiece sampling instrumentation is not used for
adjusting the respirator (for example, overtightening the
QLFT.)
straps), until a passing fit test is finally achieved. Offering a
7.5.7 Respirators Used for QNFT:
reasonable assortment of respirator types or sizes or both
7.5.7.1 Respirators used for QNFT shall allow in-facepiece
should eliminate the inclination to force-fit.
sampling. This can be accomplished by:
(1)Using a fit test sampling adapter on an individually
7.6.2 Selecting a Suitable Respirator for the Fit Test—Initial
assigned respirator facepiece,
respiratorwearersandanyoneneedingtochangesizeormodel
(2)Using a fit test sampling adapter on a surrogate respi-
of respirators shall select from the assortment offered. The
rator facepiece, or
respirator assortment shall include a sufficient number of
(3)Using a permanently probed surrogate respirator face-
respirator models and sizes so that all respirator wearers can
piece.
obtain an acceptable fit. The selection should be based on
7.5.7.2 Respirators Temporarily Modified with Adapters—
comfort and results of user seal checks, as well as personal
Fit test sampling adapters used for QNFT shall be completely
preferences.Theyshallbefittestedwiththerespiratorthatthey
removed and the respirator restored to its NIOSH-approved
select.
configuration before that respirator is used for respiratory
7.6.2.1 Respirator comfort is an important factor in wearer
protection.
acceptance. Other factors that influence wearer acceptance
7.5.7.3 Permanently Probed Surrogate Respirator
includebreathingresistance,impairmentofvision,impairment
Facepieces—Respirators used for QNFT may be permanently
of communications, and respirator weight. Respirators with
probed to provide a sampling port for the purpose of obtaining
greater wearer acceptance are likely to be worn.
an in-facepiece sample. Permanently probed respirators shall
7.6.2.2 Repeat fit testing can be accomplished on the same
not be used for respiratory protection unless the respirator is
NIOSH approved in the probed configuration. make, model, style, and size respirator without repeating the
selection process if the wearer still finds that respirator
7.5.8 Sampling for Aerosol Systems—In-facepiece aerosol
sampling devices shall be designed and used such that the acceptable.
F3537 − 21
7.6.2.3 If fit testing shows that a person can obtain an 7.7.3.5 Persons passing a fit test shall be issued a facepiece
acceptable fit with two or more models of the selected class of identicaltotheoneusedforthefittestorthemodelrepresented
respirator, then the person should be permitted to use the by the surrogate facepiece used for the fit test.
preferred respirator model. 7.7.4 Required Fit Factor—Refer toANSI/ASSE Z88.2, 29
CFR 1910.134, or other applicable regulatory standards for
7.6.3 Comfort Assessment Period—Initialrespiratorwearers
required fit factors.
andanyonewhochangesthemodelorbrandofrespiratorshall
weartherespiratorforacomfortassessmentperiodofapproxi-
8. Quantitative Fit Test (QNFT) Methods
mately 5min immediately before the fit test. If necessary, the
person being fit tested may make adjustments to achieve a
8.1 This section contains the QNFT methods that were
comfortable fit during this period.
found to be acceptable when this guide was published. These
7.6.3.1 Experienced respirator wearers previously fit tested
specific instructions were written to document the important
with the same respirator may bypass the comfort assessment
requirements of the method without being tied to a specific
period.Wearingarespiratorforaperiodoftimebeforethestart
manufacturer’s instrumentation.As such, the instructions may
of the fit test may be more representative of respirator use
not be specific enough to be used as the only guidance for fit
conditions.
testoperators.Itwillusuallybenecessarytousetheinstrument
7.6.3.2 The comfort assessment period allows the respirator
manufacturer’s detailed instructions to perform a specific
wearer time to determine if the respirator is truly comfortable
quantitative fit test. Follow the manufacturer’s recommenda-
or not and make any necessary adjustments. Discomfort may
tions for periodic service and calibration.
become apparent only after the respirator is worn for a period
8.2 Generated Aerosol Quantitative Fit Test Procedure:
of time. For example, overtightened straps may not be noticed
8.2.1 Operating Principles—An aerosol challenge agent is
immediately. If the respirator wearer finds the comfort of the
introduced into a test chamber that surrounds the head and
respirator to be unacceptable at any time, they shall be given
shoulders, or the entire body, of the respirator wearer. An
the opportunity to try another respirator.
instrument is used to measure concentration of the challenge
7.6.3.3 Itiscriticalthatallrespiratorwearersdonandadjust
aerosol outside (C ) and inside (C ) the respirator, while the
out in
their respirators just as they would when wearing it for
person being fit tested performs a series of exercises designed
respiratory protection.
to stress the face seal in ways that approximate anticipated
7.7 Test Requirements Common to All Fit Tests:
workplace conditions.
7.7.1 Fit Test Operator Requirements—The fit test shall be
8.2.1.1 The test respirator shall be equipped with filters that
administered by a fit test operator who meets the requirements
do not allow the challenge aerosol to penetrate significantly
of Section 6 and follows all the procedures in this guide.
intotherespirator.Thus,itisassumedthatallparticlessampled
7.7.2 Environmental Requirements—The following condi-
frominsidetherespiratorhaveenteredthroughafacesealleak.
tions shall be met:
8.2.1.2 The fit factor is calculated as the ratio of the two
7.7.2.1 The ability to observe and communicate with the relative aerosol concentrations:
person being fit tested at all times during the fit test,
C
out
FitFactor 5 (1)
7.7.2.2 The ability to establish and maintain an appropriate
C
in
challenge agent concentration during the test,
8.2.2 Equipment—Equipment needed for aerosol QNFT:
7.7.2.3 Exposures of persons being fit tested and fit test
8.2.2.1 Aerosol Generation and Distribution System—The
operators shall not exceed established exposure limits for any
challenge aerosol shall have a mass median aerodynamic
challenge agents used, and
diameter (MMAD) less than 1µm;
7.7.2.4 Sufficient space to complete specified fit test exer-
8.2.2.2 Aerosol detection system;
cises without interference.
8.2.2.3 Device for recording fit test results;
7.7.3 Other Requirements:
8.2.2.4 Test chamber to contain challenge aerosol;
7.7.3.1 The person being fit tested shall don the respirator
8.2.2.5 Respirator equipped with sampling probe or fit test
without physical or verbal assistance and perform a user seal
sampling adapter and appropriate filters; and
check;
8.2.2.6 Other accessories and supplies as required by the
7.7.3.2 The person being fit tested shall perform a series of
equipment manufacturer.
exercises designed to stress the respirator seal in ways that
8.2.3 Equipment Setup—Followmanufacturer’sinstructions
simulate actual workplace motions. Follow the test protocols
as necessary to:
specified in Sections 8 and 9 to conduct fit testing;
8.2.3.1 Verify that all components are assembled according
7.7.3.3 The respirator shall not be adjusted once the fit test
to the manufacturer’s instructions. This includes the hoses
exercises begin.Adjustments void the test, requiring the entire
supplyingaerosoltothetestchamberandreturningexhaustair
exercise protocol to be restarted from the beginning. An
from the chamber, sample lines, electrical connections, and so
exception is the re-donning exercise;
forth;
7.7.3.4 The person tested shall be informed of the results
8.2.3.2 Perform necessary maintenance and visual inspec-
and told that another fit test with a different respirator can be
tion;
obtained if problems are experienced with the respirator at any
time; and 8.2.3.3 Power up system and allow proper warmup;
F3537 − 21
8.2.3.4 Perform any preliminary adjustments, for example, significantly.Thus,itisassumedthatallparticlessampledfrom
sampleflow,generatorpressure,dilutionairflow,andsoforth; inside the respirator have entered though a face seal leak.
and
8.3.1.3 The fit factor is computed from the two aerosol
8.2.3.5 Allow time for the aerosol concentration to stabilize concentration measurements:
in the test chamber.
C
out
FitFactor 5 (5)
8.2.4 Conducting the Fit Test:
C
in
8.2.4.1 Enter all pertinent data into the test record as
8.3.1.4 Care shall be taken to minimize body-generated
described in Section 11,
particles inside the respirator. Since the system cannot differ-
8.2.4.2 Instruct the person being fit tested to don the
entiate between body-generated particles and ambient aerosol
respirator as trained,
penetration, this can result in erroneously low fit factors. For
8.2.4.3 Have the person being fit tested enter the test
example, particles may be released from the lungs for a period
chamber and connect the test respirator to the sample line,
of time after smoking a cigarette. Therefore, fit testing should
8.2.4.4 Perform fit test according to instrument manufac-
not be conducted within 30min of smoking.
turer instructions using the exercises specified in Section 10,
8.3.2 Equipment Needed:
and
8.3.2.1 Condensation nuclei counter QNFT instrument,
8.2.4.5 Thetestresultsshallberecordedinaccordancewith
Section 11. 8.3.2.2 Filter for diagnostic checks recommended by the
8.2.5 Interpretation of Results—The average penetration is instrument manufacturer,
thearithmeticmeanofthemeasuredpenetration(Pen)foreach
8.3.2.3 Other accessories and supplies required by instru-
exercise: ment manufacturer, and
8.3.2.4 Respiratorsequippedwithprobesorfittestsampling
Pen 1Pen 1Pen 1. Pen
1 2 3 N
AveragePenetration 5 (2)
adapters and particulate filters that do not allow the challenge
N
aerosol to penetrate significantly.
where:
8.3.3 Diagnostic Checks—The following diagnostic checks
N = number of exercises.
shall be performed at least daily. The instrument shall pass all
three checks before fit testing can begin. Refer to the manu-
8.2.5.1 The overall fit factor is calculated by: Overall FF =
facturer’s instructions for specifications and guidance.
1/Average Penetration.
8.3.3.1 Particle Check—Measure the concentration of par-
8.2.5.2 Example: Pen = 0.0015, Pen = 0.0007, Pen =
1 2 3
ticles in the environment where fit testing will be conducted to
0.0017, Pen = 0.0005, Pen = 0.0009, and Pen = 0.0011.
4 5 6
make sure that the instrument is working and within the
0.001510.000710.001710.000510.000910.0011
concentration range specified by the instrument manufacturer
AvgPen 5 (3)
to permit reliable measurements.
8.3.3.2 Zero Check—Aftertheparticlecheckissuccessfully
50.001076
completed, with the instrument in particle-counting mode,
OverallFitFactor 51⁄0.001067 5937 (4)
attach the high-efficiency particulate air (HEPA) filter to the
8.2.5.3 Whenastripchartisused,the Penforeachexercise
sample hose. Watch the particle concentration display to make
isestimatedbydrawingalinethroughthemidpointofthetrace sure it drops to near zero within the time specified by the
for that exercise. The midpoint of this line represents the
manufacturer. This confirms there are no leaks in the system.
percent penetration taking into account the range to which the
8.3.3.3 System Check—After the zero check is successfully
instrument is set.
completed,leavethefilteronthesamplehoseandperformafit
8.2.5.4 The person has passed the fit test if the overall fit
factormeasurementonthefilter.Theresultshouldcomplywith
factor equals or exceeds the required fit factor.
the manufacturer’s instructions and specifications. This con-
firms that high fit factors can be measured.
8.3 Ambient Aerosol Condensation Nuclei Counter (CNC)
8.3.4 Prepare to Fit Test:
Quantitative Fit Test Procedure:
8.3.4.1 Follow the manufacturer’s instructions to set the
8.3.1 Operating Principles—CNC instruments are capable
instrument to perform the required fit test exercise protocol;
of measuring the number concentration of particles in a given
8.3.4.2 Connecttheinstrumentsamplehosetotherespirator
aerosol sample by counting single particles. When used for
to be tested;
QNFT, the particle concentration of the challenge aerosol
8.3.4.3 Instruct the person being fit tested to don the
(C ) and the particle concentration inside the respirator (C )
out in
respirator as trained (see Section 7); and
are both measured while the person being fit tested performs a
series of exercises designed to stress the face seal in ways that 8.3.4.4 Allow the person’s breathing to purge ambient
approximate anticipated workplace conditions. particles trapped inside the respirator during donning. A half
8.3.1.1 CNC instruments typically use the particles in the facepiece will usually purge in a few breaths, while a full
ambientairasthechallengeaerosol.Thispermitstheuseofan facepiece may take a full minute.
aerosol generator, if needed, and does not require the use of a
8.3.5 Fit Testing—Initiate the instrument’s fit test cycle.
test chamber. Instruct the person being fit tested to begin and follow through
8.3.1.2 The respirator shall be equipped with particulate with the exercise protocol (see Section 10). During this
filters that do not allow the challenge aerosol to penetrate process, the instrument will sample the particle concentration
F3537 − 21
NOTE 1—The inhalation valve downstream from the test adapter
inthetestenvironmentandtheconcentrationofthoseparticles
containing the air exhaust port shall be either removed or propped open
that leak into the respirator.
during the fit test.
8.3.6 Interpretation of Results—At the completion of the fit
8.4.3 System Calibration and Operational Checks:
test,theinstrumentprovidesapass/failindicationoranumeric
8.4.3.1 Calibrate the pressure and flow rate transducers
overall fit factor result, or both, for the entire test calculated
according to manufacturer recommendations.
according to Eq 6. The person has passed the fit test if the
8.4.3.2 The pressure/flow rate relationship of the bypass
overall fit factor equals or exceeds the required fit factor.
orifice should be checked on a daily basis.
N
8.4.4 Prepare to Fit Test:
OverallFitFactor 5 (6)
1 1 1
8.4.4.1 Equip the test respirator with appropriate CNP test
1 1.
FF FF FF
1 2 N
adapter(s).
where:
NOTE 2—Inhalation valve shall be removed or propped open.
N = number of exercises,
8.4.4.2 Tell the person being fit tested to don the respirator
FF = fit factor for the first exercise,
as trained (see Section 7).
FF = fit factor for the second exercise, and
th
8.4.4.3 Select the instrument test parameters.
FF = fit factor for the N exercise.
N
8.4.5 Fit Testing:
8.3.6.1 Example: Given the following fit factors for a series
8.4.5.1 Tell the person being fit tested to take a breath and
of six exercises: FF = 666, FF = 1429, FF = 588, FF =
1 2 3 4
hold it for the duration of the measurement. The person shall
2000, FF = 1111, and FF = 909.
5 6
remain motionless in the specified head position during the
measurement.
OverallFitFactor 5 5937
1 1 1 1 1 1
8.4.5.2 It is important that the in-facepiece pressure equili-
1 1 1 1 1
666 1429 588 2000 1111 909 brates to ambient pressure before the initiation of the test.
8.4.5.3 The CNP test system is activated to establish and
(7)
maintain a negative challenge pressure in the temporarily
8.4 Controlled Negative Pressure (CNP) Quantitative Fit
sealed respirator. The exhaust flow rate required to maintain a
Test Procedure:
constantchallengepressureisaveragedoverthedurationofthe
8.4.1 Operating Principle—The CNP fit test method is
measurement and represents a direct measure of respirator
based on exhausting air from a temporarily sealed respirator.
leakage flow rate.
Measurement of the air exhaust rate required to hold the
8.4.6 Interpretation of CNP Test Results:
in-facepiece pressure constant yields a direct measure of
8.4.6.1 A CNP fit factor is calculated as the ratio of
leakage air flow into the respirator. The rate of air leakage is
inspiratory flow rate to measured leakage flow rate.
directly related to the amount of negative pressure created
8.4.6.2 At the completion of the fit test, the instrument
inside the respirator during inspiration. The primary factors
provides a pass/fail indication or a numeric overall fit factor
affecting in-facepiece negative pressure during inhalation are
result, or both, for the entire test calculated according to Eq 8.
work rate and air flow resistance through the filters/cartridges.
The person has passed the fit test if the overall fit factor equals
During CNP fit testing, in-facepiece negative challenge pres-
or exceeds the required fit factor.
sures are selected that simulate low-to-moderate work rates
rather than resting conditions. CNPFitFactor 5 IFR ⁄ LFR (8)
8.4.1.1 Air molecules are the challenge agent for a CNP fit
where:
test.Theamountofairthatleaksintotherespiratorisassumed
IFR = inspiratory flow rate associated with CNP challenge
torepresentfacesealleakage.Therateofairleakageisdirectly
pressure, and
related to the pressure differential created inside the respirator
LFR = mean leakage flow rate measured with the head held
during inspiration. The primary determinants of in-facepiece
in a motionless position at the end of each test
inspiratory pressure include work rate and air-purifying car-
exercise.
tridge resistance. CNP challenge pressures approximate in-
8.4.6.3 Example: Given a modeled inspiratory flow rate of
spiratory pressure differentials associated with low-to-
moderate work rates rather than resting conditions. 53800 mL/min (equivalent to a moderate work rate): LFR =
48 mL/min, LFR = 69 mL/min, LFR = 59 mL/min, LFR =
8.4.1.2 A CNP fit factor is calculated from the ratio of the
2 3 4
modeled inspiratory flow rate and measured leakage flow rate. 53 mL/min, and LFR = 58 mL/min.Average LFR = (LFR +
5 1
LFR +… LFR )/ N=287/5=57.4.Fitfactor=53800/57.4
Fit factors cannot be measured during exercises in controlled
2 N
negative-pressure fit testing.Therefore, measurements of face- = 937.
piece leakage are made at the end of each exercise.
9. Qualitative Fit Test (QLFT) Methods
8.4.2 Equipment Needed—Controlled negative pressure
(CNP) fit test instrument and CNP fit test adapters are the 9.1 This section contains the QLFT methods reviewed by
equipment needed. thecommitteethatwerefoundtobeacceptablewhenthisguide
8.4.2.1 Filter cartridges are replaced with leak-tight test was published. A qualitative fit test uses a person’s ability to
adapterstosealthenormalairpathwaysintotherespirator.The senseachallengeagent(suchasbytasteorsmell)todetermine
adapters are equipped with a breathing valve as well as air if respirator leakage occurs. The tests do not give a numerical
exhaust and pressure-monitoring ports. indicationoffit;nodirectmeasurementsofthechallengeagent
F3537 − 21
and leak concentrations are made. The reliability of the test (2)If the person correctly identifies which jar contains
depends upon the person’s ability to detect and indicate IAA, then the person may continue with the test. If the correct
whether the challenge agent is sensed and requires that the jar cannot be identified, the IAA fit test method shall not be
operator carefully follow the accepted test protocol. used.
9.2 Isoamyl Acetate (Banana Oil) Fit Test—The isoamyl
NOTE 5—Prevent olfactory fatigue by not allowing IAA vapor to be
acetate (IAA) fit test uses a person’s sense of smell to detect
present in the screening area. The odor screening test shall be done in a
separate area (that is, a different room) to prevent transfer of IAAvapors
leakageintotherespirator.Thepersonbeingfittestedfirstshall
from the fit-testing area.
demonstrate the ability to detect a known low (~1 ppm)
NOTE 6—A card may be prepared with instructions that the person
concentration of IAA. Next, while wearing a respirator, the
beingfittestedcanfollowtoshakethejars,removethelids,anddetermine
person enters a test enclosure with a higher (>100 ppm)
which jar smells like bananas.
concentration of IAA. If the banana-like odor of IAA is not
NOTE 7—Take care not to contaminate the blank jar(s) by switching jar
detected, the person passes the fit test and is assumed to have lids.
a fit factor of at least 100.
9.2.2 Fit Testing—The person is fit tested while wearing a
NOTE 3—Any variation from the procedure specified in the following respirator in a test enclosure containing a controlled concen-
may invalidate the results, especially changes in solution concentrations,
tration of IAA.
amount of IAA used during the test, and the size of the test enclosure.
9.2.2.1 Equipment Needed:
(Warning—The screening test and fit test shall be done in
(1)Test enclosure—A clear plastic bag approximately
separateareasthatdonotallowthetransferofIAAvaporsfrom
60cm in diameter and 150 cm long (for example, a 255-L
the fit test area to the screening area. The sense of smell is
plasticdrumliner),equippedwithaframetoholdthebagopen
adversely affected by even brief exposures to IAA. The fit test
and a suitable device or clip for holding the absorbent paper;
should be conducted immediately after the screening test.
(2)A piece of absorbent paper (for example, a paper
Review the SDS for any handling and use precautions.)
towel), approximately 15 by 12 cm.Anew piece of absorbent
9.2.1 Odor Threshold Screening—Use of the IAA fit test
paper is needed for each fit test;
method requires that the person being fit tested is able to smell
(3)Aquantityof0.75mLofIAA(reagentgrade)isneeded
low concentrations of IAA.
for each fit test; and
9.2.1.1 Equipment Required:
(4)Respirators used for testing shall be equipped with
(1)Three or more identical 1-L glass jars with metal lids
cartridges that remove organic vapors. Cartridges should be
(for example, mason canning jars);
replaced before breakthrough occurs.This could be as often as
(2)A1-mLeyedropper,syringe,orotherdevicecapableof
weekly.
dispensing in 0.1-mL increments;
9.2.2.2 Conducting the Test:
(3)Odor-free water (for example, distilled or spring water)
(1)Instruct the person being fit tested to don the respirator
at room temperature about 20 to 25°C; and
equipped with a cartridge capable of removing organic vapors
(4)IAA, reagent grade (also known as isopentyl acetate,
astrained(seeSection7).Adjusttheceilingoftheenclosureto
CAS No. 123-92-2).
a distance about 15 cm above the person’s head.
9.2.1.2 Solution Preparation:
(2)Apply 0.75 mL of reagent grade IAA to one piece of
(1)Prepare a stock solution by adding 1 mL of reagent
absorbent paper, which is folded in half. Hand it to the person
grade IAA to 800 mL water in a glass jar labeled “stock
in the enclosure, who then attaches it to the inside top of the
solution” and shake for 30s.This solution shall be prepared at
enclosure. A freshly wetted piece of absorbent paper shall be
least weekly.
used for each fit test.
(2)Label the remaining jars described in the following
(3)Wait 2 min for the IAAconcentration to stabilize in the
using a switchable identification system (for example, switch-
enclosure.
able numbers) so that only the person who conducts the fit test
(4)Instruct the person that any detection of the smell of
can identify the contents of each jar by sight.
IAA (banana-like odor) during the test is to be reported
(3)Prepare an odor test solution by placing 0.4 mL of the
immediately.
stock solution into 500 mLwater in a second jar. Close the lid,
(5)Instruct the person to begin the series of test exercises
shake, and let the jar stand for 2 min before use. This solution
according to Section 10.
is prepared daily.
(6)The fit test is failed if the person reports smelling IAA
(4)Prepare a blank jar by adding 500 mL water to one or
at any time while conducting the test exercises.At this point, a
more jars.
decision shall be made either to retest or select another
NOTE 4—More than one blank jar should be used to make it more respirator according to Section 7. In either case, the entire
difficult for someone to guess.
procedure shall be repeated (odor screening and fit testing). It
(5)Switchthejaridentificationlabelsbetweentestssothat
may take several minutes for the person being fit tested to
the same jar is not always the one that smells like bananas.
regain the ability to smell low concentrations of IAA. Do not
9.2.1.3 Odor Screening Test: repeat the fit test until the person being fit tested successfully
(1)Ask the person being fit tested to determine which jar completes the odor threshold screening test again.
smells like bananas by instructing the person to shake each jar (7)If the person being fit tested does not report smelling
briefly, remove the lid, sniff at the mouth of the jar, and recap the IAA, instruct the person to momentarily break the respira-
the lid. tor seal and inhale. If IAA is not detected after breaking the
F3537 − 21
respirator seal, the test is null and void and the reason why the (3)Sensitivity screening solution with 0.83 g sodium
person did not smell the IAAshall be identified. If the IAAis saccharin (CAS No. 128-44-9, US
...