Respirator fit test

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F.H. Varley painting of a training exercise in Seaford, England, with soldiers emerging from a gas hut wearing respirators Frederick Varley - Gas Chamber at Seaford.jpg
F.H. Varley painting of a training exercise in Seaford, England, with soldiers emerging from a gas hut wearing respirators

A respirator fit test checks if a respirator properly fits the face of a user. A fitted respirator must be able to separate a user's respiratory system from ambient air.

Contents

The test involves tightly pressing the mask against the face (without gaps) to ensure an efficient seal on the mask perimeter. Protection depends on an airtight seal, making testing necessary before entering contaminated air. Mask size and shape, correctly fitted to the user's face, provides better protection in hazardous environments. [1] Facial hair, such as beards, can interfere with proper fit. [2]

History

Fit test in the United States Navy US Navy 061220-N-8146B-001 The Safety Department uses a plastic bag to conduct respirator fit testing aboard the amphibious assault ship USS Boxer (LHD 4).jpg
Fit test in the United States Navy

The effectiveness of various types of respirators was measured in laboratories and the workplace. [3] The measurements indicated that the effectiveness of negative-pressure, tight-fitting respiratory protective devices (RPD) depends on leakage between mask and face, rather than on filters orcanisters. [4] A decrease in efficiency due to leakage occurred on a large scale during World War I, when gas masks were used to protect against chemical weapons; poor fit or poorly-situated masks could be fatal. The Russian army began to use short-term exposure to chlorine at low concentrations to solve this problem in 1917. [5] [6] Testing helped convince soldiers that their gas masks were reliable, because respirators were a novelty. [7] Industrial workers were trained in gas chambers in the USSR (in preparation for the Second World War). [8] [9] [10] [11] German firefighters used a similar test between the First and Second World Wars. [12] Diluted chloropicrin was used to test industrial gas masks, [13] and the Soviet army used chloropicrin in tents with a floor space of 16 square meters. [14]

Methods

Respirator selection and use is regulated in many countries. [15] [16] [17] Regulations often include a test of negative pressure for each individual wearer.

Fit-test methods are qualitative (QLFT) and quantitative (QNFT). Detailed descriptions are given in the US standard developed by the Occupational Safety and Health Administration (OSHA). [15] This standard regulates respirator selection and organization; Appendix A describes fit testing, and compliance with this standard is mandatory for US employers.

Qualitative

Irritant-smoke fit test US Navy 110429-N-7326M-028 Boatswain's Mate 3rd Class Shaka K. Farrier dons a respirator as irritant smoke is released into the air as part of a re.jpg
Irritant-smoke fit test

These methods use the reaction of workers to the taste or smell of a gas, vapors or aerosol if it leaks into the mask. Such reactions are subjective, requiring the subject to report results honestly. A qualitative fit test begins with a non-respirator sampling of the substance of choice to verify that the subject can detect it accurately. Such substances include:

Quantitative

TSI PortaCount Plus, a device for ambient aerosol fit testing Kolichestvennaia proverka izoliruiushchikh svoistv QLFT priborom PortaCount Plus.jpg
TSI PortaCount Plus, a device for ambient aerosol fit testing
Air Techniques International TDA-99M, used for generated-aerosol fit testing US Navy 031205-N-6213R-009 Sailors aboard the aircraft carrier USS John C. Stennis (CVN 74) don MCU-2P gas masks under a respirator testing shroud to assess for proper fit.jpg
Air Techniques International TDA-99M, used for generated-aerosol fit testing

Concentrations of a control substance (challenge agent) inside and outside a mask can be measured, determining the flow rate of air under the mask. Quantitative methods are more accurate and reliable than qualitative methods because they do not rely on subjective sensing of a challenge agent. Unlike qualitative methods, quantitative methods provide a data-based, defensible metric.

Ambient aerosol method

An aerosol test measures internal and external aerosol concentrations. The aerosol can be artificial or a natural, atmospheric component. The ratio of external to internal concentration is known as the fit factor (FF). [19] U.S. law requires employers to offer employees masks with an adequate fit factor. For half face-piece masks (used when the concentration of harmful substances is not more than 10 PEL), the fit factor must be at least 100; for full face masks (not more than 50 PEL), the fit factor must be at least 500. The safety factor of 10 compensates for the difference between testing and workplace conditions. To use an atmospheric aerosol, a PortaCount or AccuFIT device is needed. These devices increase the size of the smallest particles through vapor condensation (condensation particle counting, or CPC), and determines their concentration by count. Aerosols include sodium chloride and calcium carbonate. This method is standard for determining respirator fit for users in healthcare settings and research laboratories. [20] [21] [22] [23]

OSHA has approved a fast fit protocol which enables AAC/CPC (ambient aerosol concentration/condensation particle counting) to be performed in less than three minutes. The major advantage of the AAC/CPC method is that the test subject is moving and breathing while the fit factor is measured, better replicating actual conditions.

Flow (pressure) methods

Flow methods are a more recent development. When a worker inhales, some aerosol is deposited in their respiratory system, lowering the exhaled concentration. During inhalation leaked unfiltered air trickles under the mask, before mixing with air inside the mask. If such a stream collides with the sampling probe, the measured concentration becomes higher than the actual value. But if the trickle does not come into contact with a probe the concentration becomes lower.

Control Negative Pressure (CNP) directly measures the volume of air leaking into the respirator, and this is converted into a fit factor. Using a challenge pressure of 53.8 – 93.1 L/min, the CNP devices stress the mask as a user would while breathing heavily under extreme physical conditions. A CNP device manufacturer claims that using air as a standard challenge agent provides a more rigorous test of mask fit than an aerosol agent. If air leaks into a respirator then, particles, vapors, or gas contaminants may also leak in. Redon protocols allow a fit test to be performed in under 3 minutes.[ citation needed ] The CNP Method of fit testing is OSHA, NFPA and ISO certified (among others).

Dichot method differs from CNP in that common filters are installed on the mask and air is quickly pumped out from the mask, creating a vacuum. The negative pressure depends on the filter resistance and leak rate. Filter resistance is measured with a sealed attachment of the mask to a dummy, allowing calculation of the leak rate through the gaps.

Industry

U.S. law began requiring employers assign and test a mask for each employee before assignment to positions requiring respirator use and thereafter every 12 months, and optionally, in case of circumstances that could affect fit (injury, tooth loss, etc.). [18] Other countries have similar requirements. [17] [24] A U.S. study showed almost all large enterprises complied with these regulations. About half of enterprises with fewer than 10 workers were non-compliant in 2001. [25] Such violations may be due to the cost of quantitative fit test equipment, qualitative fit test inaccuracy, and small organizations having fewer rigorous compliance processes.

Comparison

The main advantage of qualitative fit tests is low equipment cost, while their main drawback is their modest precision, and they are not sensitive enough for masks for atmospheres exceeding 10 PEL. To reduce the risk of choosing a poorly fitting respirator, the mask needs a sufficient fitting characteristic. Multiple masks must be examined to find the "most reliable", although poor test protocols may give incorrect results. Re-checks require time and increase costs. In 2001, the most common QLFT was irritant smoke and saccharin, but in 2004, NIOSH advised against using irritant smoke.

CNP is a relatively inexpensive and fast quantitative method. [26] However, disposable filtering face-piece mask (such as the N95, N99, and N100 masks) cannot be tested with CNP. Fit tests with an atmospheric aerosol may be used on any respirator, but the cost of earlier devices (PortaCount) and the duration of the test was slightly greater than CNP. However the newer OSHA Fast Fit Protocols for CNC methods, and newer instruments, have made all quantitative fit test devices equivalent in price and speed. The CNP method has at present about 15% of the fit test market in industry. [25] The Current CNC instruments are the PortaCount 8040 and the AccuFIT 9000.

User seal checks and respirator training should be done before fit testing. Obuchenie ispol'zovaniiu SIZOD (proverka pravil'nosti odevaniia izbytochnym davleniem).jpg
User seal checks and respirator training should be done before fit testing.
Fit test methods for various masks [15] [27] [28]
Fit test methodRespirator typesDevices for testing
Filtering half facepieceElastomeric half facepiece respirators and elastomeric full facepiece mask, used in workplaces with concentrations of contaminants up to 10 PELElastomeric full facepiece mask, used in workplaces with concentrations of contaminants up to 50 PEL
Qualititative fit test methods
Isoamyl acetateUnlikely to pass [a] YesNoAllegro-0202 et al.
SaccharinYesYesNo3М FT-10 et al.
BitrexYesYesNo3М FT-30 et al.
Irritant smoke [b] Class-100 filters only [28] YesNoAllegro-2050, VeriFit, RAE 10-123-01 et al.
Quantitative fit test methods
Control Negative Pressure (CNP) [c] Impossible to pass [d] YesYesFitTester 3000 (DNI Nevada/OHD), Quantifit (OHD)
Ambient Aerosol method (CPC)YesYesYesPortaCount, Accufit 9000
Generated Aerosol method (Aerosol Photometer)Oil-resistant filters only [e] YesYesTDA-99M, TSI 8587A
  1. ↑ Although called 'Banana oil,' implying it could be used with oil resistant filters, the protocol requires organic vapor cartridges, according to the US Navy. [28] Organic vapor cartridges are not found on filtering facepiece respirators.
  2. ↑ Not recommended by NIOSH. [29]
  3. ↑ CNP with modeled breathing rate. The status of Quantafit (Dynatech Frontier) CNP modeled decay rate is unknown. [30]
  4. ↑ CNP machines cannot test respirators where the entire assembly is penetrable by air, like a filtering facepiece.
  5. ↑ Generated aerosols use DOP or PAO as a test agent, similar to the oil used during initial respirator approval. [28]

References

  1. ↑ Ziqing, Zhuang; Christopher C. Coffey; Paul A. Jensen; Donald L. Campbell; Robert B. Lawrence; Warren R. Myers (2003). "Correlation Between Quantitative Fit Factors and Workplace Protection Factors Measured in Actual Workplace Environments at a Steel Foundry". American Industrial Hygiene Association Journal. 64 (6): 730–738. doi:10.1080/15428110308984867. ISSN   1542-8117. PMID   14674806.
  2. ↑ Cichowicz, Jaclyn Krah; Shaffer, Ron; Shamblin, Markee (2 November 2017). "To Beard or not to Beard? That's a good Question!". NIOSH Science Blog. CDC. Retrieved 2020-02-27.
  3. ↑ Кириллов, Владимир; Филин АС; Чиркин АВ (2014). "Обзор результатов производственных испытаний средств индивидуальной защиты органов дыхания (СИЗОД)" . Toksikologicheskiy Vestnik (in Russian). 6 (129): 44–49. doi: 10.17686/sced_rusnauka_2014-1034 . ISSN   0869-7922. Translation in English (in Wikisource): The Overview of Industrial Testing Outcome of Respiratory Organs Personal Protection Equipment
  4. ↑ Lenhart, Steven; Donald L. Campbell (1984). "Assigned protection factors for two respirator types based upon workplace performance testing". The Annals of Occupational Hygiene. 28 (2): 173–182. doi:10.1093/annhyg/28.2.173. ISSN   1475-3162. PMID   6476685.
  5. ↑ Фигуровский, Николай (1942). Очерк развития русского противогаза во время империалистической войны 1914—1918 гг (in Russian). Moscow, Leningrad: Издательство Академии наук СССР. p. 97.
  6. ↑ Болдырев, Василий (1917). Краткое практическое наставление к окуриванию войск (in Russian) (2 ed.). Moscow: Учеб.-фронтовый подотд. при Отд. противогазов В.З. и Г.С. p. 34.
  7. ↑ Чукаев К.И. (1917). Ядовитые газы (Наставление по противогазовому делу для инструкторов противогазовых команд, унтер-офицеров, а также для всех грамотных воинск. чинов) (in Russian). Kazan: типо-лит. Окр. штаба. p. 48.
  8. ↑ Митницкий, Михаил; Свикке Я.; Низкер С. (1937). В противогазах на производстве (in Russian). Moscow: ЦК Союза Осоавиахим СССР. p. 64.
  9. ↑ П. Кириллов, ed. (1935). Противогазные тренировки и камерные упражнения в атмосфере ОВ (in Russian). Moscow: Издание Центрального Совета ОСОАВИАХИМ СССР. p. 35.
  10. ↑ Достаточно ли ловок? // Новый горняк : Журнал. — Харьков, 1931. — В. 16
  11. ↑ Ковалев Н. (1944). Общие правила № 106 по уходу, хранению и работы в изолирующих, фильтрующих и шланговых промышленных противогазах, уход и работа на кислородном насосе (in Russian). Лысьва: Камский целлюлоз.-бум. комбинат. p. 106.
  12. ↑ Вассерман М. (1931). Дыхательные приборы в промышленности и в пожарном деле (in Russian). Moscow: Издательство Народного Комиссариата Внутренних Дел РСФСР. pp. 42, 207, 211, 221.
  13. ↑ Тарасов, Владимир; Кошелев, Владимир (2007). Просто о непростом в применении средств защиты органов дыхания (in Russian). Perm: Стиль-МГ. p. 279. ISBN   978-5-8131-0081-9.
  14. ↑ Чугасов АА (1966). "5 Проверка подбора лицевой части и исправности противогаза". Наставление по пользованию индивидуальными средствами защиты (in Russian). Moscow: Военное издательство Министерства обороны СССР. pp. 65–70.
  15. 1 2 3 US OSHA Standard 29 Code of Federal Register 1910.134 "Respiratory protection". Appendix A "Fit Testing Procedures"
  16. ↑ British Standard BS 4275-1997 "Guide to implementing an effective respiratory protective device programme"
  17. 1 2 DIN EN 529-2006. Respiratory protective devices - Recommendations for selection, use, care and maintenance - Guidance document; German version EN 529:2005
  18. 1 2 Bollinger, Nancy; Schutz, Robert; et al. (1987). A Guide to Industrial Respiratory Protection. NIOSH-Issued Publications, DHHS (NIOSH) Publication No. 87-116. Cincinnati, OH: National Institute for Occupational Safety and Health. doi:10.26616/NIOSHPUB87116.
  19. 1 2 Bollinger, Nancy; et al. (October 2004). NIOSH Respirator Selection Logic. NIOSH-Issued Publications, DHHS (NIOSH) Publication No. 2005-100. Cincinnati, OH: National Institute for Occupational Safety and Health. doi:10.26616/NIOSHPUB2005100.
  20. ↑ Lam, S.C.; Lee, J.K.L.; Yau, S.Y.; Charm, C.Y.C. (March 2011). "Sensitivity and specificity of the user-seal-check in determining the fit of N95 respirators". Journal of Hospital Infection. 77 (3): 252–256. doi:10.1016/j.jhin.2010.09.034. PMC   7114945 . PMID   21236516.
  21. ↑ Lam, Simon Ching; Lee, Joseph Kok Long; Lee, Linda Yin King; Wong, Ka Fai; Lee, Cathy Nga Yan (2 January 2015). "Respiratory Protection by Respirators: The Predictive Value of User Seal Check for the Fit Determination in Healthcare Settings". Infection Control & Hospital Epidemiology. 32 (4): 402–403. doi:10.1086/659151. PMID   21460496.
  22. ↑ Lam, Simon C.; Lui, Andrew K.F.; Lee, Linda Y.K.; Lee, Joseph K.L.; Wong, K.F.; Lee, Cathy N.Y. (May 2016). "Evaluation of the user seal check on gross leakage detection of 3 different designs of N95 filtering facepiece respirators". American Journal of Infection Control. 44 (5): 579–586. doi:10.1016/j.ajic.2015.12.013. PMC   7115279 . PMID   26831273.
  23. ↑ Suen, Lorna K.P.; Yang, Lin; Boss, Suki S.K.; Fung, Keith H.K.; Boost, Maureen V.; Wu, Cynthia S.T.; Au-Yeung, Cypher H.; O'Donoghue, Margaret (September 2017). "Reliability of N95 respirators for respiratory protection before, during, and after nursing procedures". American Journal of Infection Control. 45 (9): 974–978. doi:10.1016/j.ajic.2017.03.028. PMID   28526306.
  24. ↑ HSE 282/28 "FIT TESTING OF RESPIRATORY PROTECTIVE EQUIPMENT FACEPIECES"
  25. 1 2 U.S. Department of Labor, Bureau of Labor Statistics (2003). Respirator Usage in Private Sector Firms (PDF). Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health. pp. 138–142.
  26. ↑ Crutchfield, Clifton; Richard W. Murphy; Mark D. Van Ert (1991). "A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using fixed leaks". American Industrial Hygiene Association Journal. 52 (6): 249–251. doi:10.1080/15298669191364677. ISSN   1542-8117. PMID   1858667.
  27. ↑ Charles Jeffress (1998). OSHA Instruction CPL 02-00-120 "Inspection procedures for the Respiratory Protection Standard" 09/25/1998 - VII. Inspection Guidelines for the Standard on Respiratory Protection - G. Fit Testing
  28. 1 2 3 4 "Respirator Fit Testing" (PDF).
  29. ↑ "Despite benefits in testing and observation, there are many risks to smoke tubes".
  30. ↑ "Acceptability of New Technology Respirator Fit Testing Devices" (PDF).
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