respirator fit test

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

The test involves tightly pressing the mask flush 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.

Facial hair such as beards can interfere with proper fit.

History

The effectiveness of various types of respirators was measured in laboratories and in the workplace. These measurements showed that in practice, the effectiveness of negative pressure tight fitting respiratory protective devices (RPD) depends on leakage between mask and face, rather than the filters/canisters. This decrease in efficiency due to leakage manifested 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. Such testing helped convince the soldiers that their gas masks were reliable - because respirators were a novelty. Later, industrial workers were trained in gas chambers in the USSR (in preparation for the Second World War), and late'. German firefighters used a similar test between the First and Second World Wars. Diluted chloropicrin was used to test industrial gas masks. The Soviet Army used chloropicrin in tents with a floor space of 16 square meters.

Fit test methods

Respirator selection and use is regulated in many countries. Regulations often include a test of negative pressure mask for each individual wearer.

Qualitative and quantitative fit test methods (QLFT & QNFT) exist. Detailed descriptions are given in the US standard, developed by the Occupational Safety and Health Administration OSHA. This standard regulates respirator selection and organization (Appendix A describes fit testing). Compliance with this standard is mandatory for US employers.

Qualitative

These methods use the reaction of workers to the taste or smell of a special material (if it leaks into mask) - gas, vapors or aerosols. Such reactions are subjective, requiring the subject to report results honestly. A qualitative fit test starts with an unfiltered/non-respirator sampling of the substance of choice to verify that the subject can detect it accurately. Substances include:

* Isoamyl acetate—This substance has the smell of bananas. It is used only for fit testing of elastomeric masks.
* Saccharin— Mixed with water and aerosolized, saccharin's sweet taste is used to test elastomeric and filtering respirator masks. The subject breathes through the mouth, slightly sticking out the tongue.
* Denatonium— A substance with a bitter taste that can be used to detect gaps. It is mixed with water and sprayed in the same manner as the above materials.

* Irritant smoke— Irritates mucous membranes resulting in discomfort, coughing, sneezing, etc. NIOSH recommended discontinuing this method, as exposure may significantly exceed the Permissible Exposure Limit (e.g., in the presence of high humidity).

Quantitative

Equipment can determine concentrations of a control substance (challenge agent) inside and outside the mask or determine 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 the challenge agent. Unlike qualitative methods, quantitative methods provide a data-based, defensible metric.

Ambient aerosol method

An aerosol test measures the internal and external aerosol concentrations. The aerosol can be artificial, or a natural atmospheric component. The ratio of external to internal concentration is the fit factor (FF). U.S. law requires employers offer employees masks with sufficient 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; and 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 one needs a PortaCount or AccuFIT device. These devices increase the size of the smallest particles through a process of vapor condensation (Condensation Particle Counting or CPC), and then determines their concentration (by count). Aerosols include: sodium chloride, calcium carbonate, etc. This method is standard for determining respirator fit for users in healthcare settings and research laboratories.

Recently OSHA approved a Fast Fit Protocol which enables the AAC/CPC (Ambient Aerosol Concentration/Condensation Particle Counting) method 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 being measured. This better replicates the actual conditions the respirator will be used in.

Generated aerosol method

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.
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.). Other countries have similar requirements. 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. 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. 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. The Current CNC instruments are the PortaCount 8040 and the AccuFIT 9000.

References

{{reflist, colwidth=30em, refs=
{{cite book, last=Фигуровский, first=Николай , title=Очерк развития русского противогаза во время империалистической войны 1914—1918 гг. , year=1942, publisher=Издательство Академии наук СССР, location=Moscow, Leningrad, language=ru, page=97

{{cite book , last=Болдырев , first=Василий , title=Краткое практическое наставление к окуриванию войск , edition=2 , year=1917 , publisher=Учеб.-фронтовый подотд. при Отд. противогазов В.З. и Г.С , location=Moscow , language=ru , page=34

{{cite book, last=Чукаев К.И., title=Ядовитые газы (Наставление по противогазовому делу для инструкторов противогазовых команд, унтер-офицеров, а также для всех грамотных воинск. чинов), year=1917, publisher=типо-лит. Окр. штаба , location=Kazan, language=ru, page=48

{{cite book, last1=Митницкий, first1=Михаил , last2=Свикке Я., last3=Низкер С., title=В противогазах на производстве, year=1937, publisher=ЦК Союза Осоавиахим СССР , location=Moscow, language=ru, page=64

{{cite book, editor=П. Кириллов , title=Противогазные тренировки и камерные упражнения в атмосфере ОВ, year=1935, publisher=Издание Центрального Совета ОСОАВИАХИМ СССР, location=Moscow, language=ru, page=35

{{cite book, last=Вассерман М., title=Дыхательные приборы в промышленности и в пожарном деле, year=1931, publisher=Издательство Народного Комиссариата Внутренних Дел РСФСР, location=Moscow, language=ru, pages=42, 207, 211, 221

{{cite book, last=Ковалев Н., title=Общие правила № 106 по уходу, хранению и работы в изолирующих, фильтрующих и шланговых промышленных противогазах, уход и работа на кислородном насосе , year=1944, publisher=Камский целлюлоз.-бум. комбинат , location=Лысьва, language=ru, page=106

{{cite book, last1=Тарасов, first1=Владимир, last2=Кошелев, first2=Владимир, title=Просто о непростом в применении средств защиты органов дыхания, year=2007, publisher=Стиль-МГ , location=Perm, language=ru, isbn=978-5-8131-0081-9, page=279

{{cite book, last=Чугасов АА, title=Наставление по пользованию индивидуальными средствами защиты, year=1966, publisher=Военное издательство Министерства обороны СССР, location=Moscow, language=ru, pages=65–70, chapter=5 Проверка подбора лицевой части и исправности противогаза

{{cite journal, last=Ziqing, first=Zhuang , author2=Christopher C. Coffey , author3=Paul A. Jensen , author4=Donald L. Campbell , author5=Robert B. Lawrence , author6=Warren R. Myers, year=2003, title=Correlation Between Quantitative Fit Factors and Workplace Protection Factors Measured in Actual Workplace Environments at a Steel Foundry, journal=American Industrial Hygiene Association Journal, volume=64, issue=6, pages=730–738, issn=1542-8117, doi=10.1080/15428110308984867, pmid=14674806

US OSHA Standard 29 Code of Federal Register 1910.134 "Respiratory protection"
Appendix A "Fit Testing Procedures"
/ref>

{{cite book, last1=Bollinger, first1=Nancy, last2=Schutz, first2=Robert, title=A Guide to Industrial Respiratory Protection, url=https://www.cdc.gov/niosh/docs/87-116/, series=NIOSH-Issued Publications, DHHS (NIOSH) Publication No. 87-116, year=1987, publisher=National Institute for Occupational Safety and Health, location=Cincinnati, OH , display-authors=etal, doi=10.26616/NIOSHPUB87116

Достаточно ли ловок? // Новый горняк : Журнал. — Харьков, 1931. — В. 16

{{cite book, last1=Bollinger, first1=Nancy , title=NIOSH Respirator Selection Logic, url=https://www.cdc.gov/niosh/docs/2005-100/, series=NIOSH-Issued Publications, DHHS (NIOSH) Publication No. 2005-100, date=October 2004, publisher=National Institute for Occupational Safety and Health, location=Cincinnati, OH , display-authors=etal, doi=10.26616/NIOSHPUB2005100

{{cite book, last=U.S. Department of Labor, Bureau of Labor Statistics, title=Respirator Usage in Private Sector Firms, url=https://www.cdc.gov/niosh/docs/respsurv/pdfs/respsurv2001.pdf, year=2003, publisher=U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, location=Morgantown, WV, pages=138–142

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

{{cite journal, last=Crutchfield, first=Clifton, author2=Richard W. Murphy , author3= Mark D. Van Ert, year=1991, title=A comparison of controlled negative pressure and aerosol quantitative respirator fit test systems by using fixed leaks, journal=American Industrial Hygiene Association Journal, volume=52, issue=6, pages=249–251, issn=1542-8117, doi=10.1080/15298669191364677, pmid=1858667

HSE 282/28 "FIT TESTING OF RESPIRATORY PROTECTIVE EQUIPMENT FACEPIECES"

DIN EN 529-2006. Respiratory protective devices - Recommendations for selection, use, care and maintenance - Guidance document; German version EN 529:2005

{{cite journal, last=Lenhart, first=Steven, author2=Donald L. Campbell, year=1984, title=Assigned protection factors for two respirator types based upon workplace performance testing, journal=The Annals of Occupational Hygiene, volume=28, issue=2, pages=173–182, issn=1475-3162, doi=10.1093/annhyg/28.2.173, pmid=6476685

{{cite journal, last=Кириллов, first=Владимир , author2=Филин АС , author3=Чиркин АВ, year=2014, title=Обзор результатов производственных испытаний средств индивидуальной защиты органов дыхания (СИЗОД), journal=Toksikologicheskiy Vestnik, volume=6 , issue=129, pages=44–49, issn=0869-7922, doi=10.17686/sced_rusnauka_2014-1034, url=http://www.toxreview.ru, language=ru, url-access=subscription, doi-access=free Translation in English ''(in Wikisource)'': The Overview of Industrial Testing Outcome of Respiratory Organs Personal Protection Equipment

British Standard BS 4275-1997 "Guide to implementing an effective respiratory protective device programme"

{{cite journal , last1=Lam , first1=S.C. , last2=Lee , first2=J.K.L. , last3=Yau , first3=S.Y. , last4=Charm , first4=C.Y.C. , title=Sensitivity and specificity of the user-seal-check in determining the fit of N95 respirators , journal=Journal of Hospital Infection , date=March 2011 , volume=77 , issue=3 , pages=252–256 , doi=10.1016/j.jhin.2010.09.034, pmid=21236516, pmc=7114945

{{cite journal , last1=Lam , first1=Simon Ching , last2=Lee , first2=Joseph Kok Long , last3=Lee , first3=Linda Yin King , last4=Wong , first4=Ka Fai , last5=Lee , first5=Cathy Nga Yan , title=Respiratory Protection by Respirators: The Predictive Value of User Seal Check for the Fit Determination in Healthcare Settings , journal=Infection Control & Hospital Epidemiology , date=2 January 2015 , volume=32 , issue=4 , pages=402–403 , doi=10.1086/659151, pmid=21460496

{{cite journal , last1=Lam , first1=Simon C. , last2=Lui , first2=Andrew K.F. , last3=Lee , first3=Linda Y.K. , last4=Lee , first4=Joseph K.L. , last5=Wong , first5=K.F. , last6=Lee , first6=Cathy N.Y. , title=Evaluation of the user seal check on gross leakage detection of 3 different designs of N95 filtering facepiece respirators , journal=American Journal of Infection Control , date=May 2016 , volume=44 , issue=5 , pages=579–586 , doi=10.1016/j.ajic.2015.12.013, pmid=26831273, pmc=7115279

{{cite journal , last1=Suen , first1=Lorna K.P. , last2=Yang , first2=Lin , last3=Boss , first3=Suki S.K. , last4=Fung , first4=Keith H.K. , last5=Boost , first5=Maureen V. , last6=Wu , first6=Cynthia S.T. , last7=Au-Yeung , first7=Cypher H. , last8=O'Donoghue , first8=Margaret , title=Reliability of N95 respirators for respiratory protection before, during, and after nursing procedures , journal=American Journal of Infection Control , date=September 2017 , volume=45 , issue=9 , pages=974–978 , doi=10.1016/j.ajic.2017.03.028, pmid=28526306

External links

* Jeff Wee
Be Prepared with a Complete Respiratory Protection Plan
July 2009. Managing Infection Control, 6pp

Safety equipment
Respirators

fr:Masque à gaz#Étanchéité