Frederick Varley - Gas Chamber at Seaford

A respirator fit test checks whether a

respirator A respirator is a device designed to protect the wearer from inhaling hazardous atmospheres including fumes, vapours, gases and particulate matter such as dusts and airborne pathogens such as viruses. There are two main categories of respir ...

properly fits the face of someone who wears it. The fitting characteristic of a respirator is the ability of the mask to separate a worker's

respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...

from ambient air. This is achieved by tightly pressing the mask flush against the face (without gaps) to ensure an efficient seal on the mask perimeter. Because wearers cannot be protected if there are gaps, it is necessary to test the fit before entering into contaminated air. Multiple forms of the test exist. Scientific studies have shown that if the mask size and shape is correctly fitted to the employees’ face, they will be better protected in hazardous workplaces. Facial hair such as a

beard A beard is the hair that grows on the jaw, chin, upper lip, lower lip, cheeks, and neck of humans and some non-human animals. In humans, usually pubescent or adult males are able to grow beards. Throughout the course of history, societal at ...

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 World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

, when

gas mask A gas mask is a mask used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft tissues of the face. Most gas mask ...

s were used to protect against

chemical weapon A chemical weapon (CW) is a specialized munition that uses chemicals formulated to inflict death or harm on humans. According to the Organisation for the Prohibition of Chemical Weapons (OPCW), this can be any chemical compound intended as a ...

s. Poor fit or poorly situated masks could be fatal. The Russian army began to use short-term exposure to

chlorine Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...

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 chamber A gas chamber is an apparatus for killing humans or other animals with gas, consisting of a sealed chamber into which a poisonous or asphyxiant gas is introduced. Poisonous agents used include hydrogen cyanide and carbon monoxide. Histor ...

s in the

USSR The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, it was nominally a federal union of fifteen nationa ...

(in preparation for the

Second World War World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

), and late'. German

firefighter A firefighter is a first responder and rescuer extensively trained in firefighting, primarily to extinguish hazardous fires that threaten life, property, and the environment as well as to rescue people and in some cases or jurisdictions also ...

s used a similar test between the First and

Second World Wars World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. Diluted

chloropicrin Chloropicrin, also known as PS and nitrochloroform, is a chemical compound currently used as a broad-spectrum antimicrobial, fungicide, herbicide, insecticide, and nematicide. It was used as a poison gas in World War I. Its chemical structural for ...

was used to test industrial gas masks. The Soviet Army used chloropicrin in tents with a floor space of 16 square meters. The US army provides military training using an irritating smoke.

Fit test methods

Respirator selection and use are regulated by national legislation in many countries. These requirements 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 Occupational Safety and Health Administration

OSHA OSHA or Osha may refer to: Work * Occupational Safety and Health Administration, a federal agency of the United States that regulates workplace safety and health * Occupational Safety and Health Act (United States) of 1970, a federal law in the Un ...

. 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 Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma). A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...

vapor In physics, a vapor (American English) or vapour (British English and Canadian English; American and British English spelling differences#-our, -or, see spelling differences) is a substance in the gas phase at a temperature lower than its critic ...

s or

aerosol An aerosol is a suspension (chemistry), suspension of fine solid particles or liquid Drop (liquid), droplets in air or another gas. Aerosols can be natural or Human impact on the environment, anthropogenic. Examples of natural aerosols are fog o ...

s. Such reactions are subjective, making this test dependent on the subject reporting 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 Isoamyl acetate, also known as isopentyl acetate, is an organic compound that is the ester formed from isoamyl alcohol and acetic acid, with the molecular formula C7H14O2.It is a colorless liquid that is only slightly soluble in water, but very s ...

—This substance has the smell of bananas. It is used only for fit testing of elastomeric masks. *

Saccharin Saccharin (''aka'' saccharine, Sodium sacchari) is an artificial sweetener with effectively no nutritional value. It is about 550 times as sweet as sucrose but has a bitter or metallic aftertaste, especially at high concentrations. Saccharin is u ...

—An aerosol of an

aqueous solution An aqueous solution is a solution in which the solvent is water. It is mostly shown in chemical equations by appending (aq) to the relevant chemical formula. For example, a solution of table salt, or sodium chloride (NaCl), in water would be re ...

saccharin Saccharin (''aka'' saccharine, Sodium sacchari) is an artificial sweetener with effectively no nutritional value. It is about 550 times as sweet as sucrose but has a bitter or metallic aftertaste, especially at high concentrations. Saccharin is u ...

(''Sodium saccharin'') is used to test both an elastomeric and filtering respirator masks. Saccharin is perceived as sweet. The subject breathes through the mouth, slightly sticking out the tongue. The aerosol is created using a simple aerosol generator with rubber "pear", which is compressed manually. *

Denatonium Denatonium, usually available as denatonium benzoate (under trade names such as Denatrol, BITTERANT-b, BITTER+PLUS, ''Bitrex'', and ''Aversion'') and as denatonium saccharide (BITTERANT-s), is the most bitter chemical compound known, with bitternes ...

—A substance with a bitter taste can be used to detect gaps. It is mixed with water and sprayed in the same manner as the above materials. * Irritant smoke—An irritating smoke causes irritation of the

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

s—resulting in discomfort, coughing, sneezing, etc.

NIOSH The National Institute for Occupational Safety and Health (NIOSH, ) is the United States federal agency responsible for conducting research and making recommendations for the prevention of work-related injury and illness. NIOSH is part of the C ...

recommended discontinuing this method, because research showed that exposure may significantly exceed the

Permissible Exposure Limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational S ...

(PEL) (e.g., in the presence of high humidity).

Quantitative

Equipment can determine the concentrations of a control substance (challenge agent) inside and outside the mask or to determine the flow rate of air flowing 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. Perhaps the most important consideration is the fact that unlike qualitative methods, the quantitative methods provide a data-based, defensible metric.

Aerosol methods

An aerosol test is carried out by measuring the internal and external

concentrations. The aerosol can be artificially created (to check the mask), or a natural atmospheric component. The ratio of external concentration to the concentration under the mask is called a fit factor (FF). U.S. law requires employers to offer employees a mask with large enough fit factor. For half face-piece masks (used when the concentration of harmful substances is not more than 10 PEL), the fit factor should not be less than 100; and for full face masks (not more than 50 PEL), the fit factor should not be less than 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 may be:

sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35.45 g ...

, calcium carbonate, and others. This method has been used as gold standard for determining whether or not a given respirator fits a healthcare worker 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 dynamic measurement is more representative of the actual conditions under which the respirator is used in the workplace.

Flow (pressure) methods

These methods appeared later than aerosol. When a worker inhales, a portion of the aerosol is deposited in their respiratory organs, and the concentration measured during the exhalation becomes lower than during inhalation. During inhalation leaked unfiltered air trickles under the mask, not actually mixing with air under 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) fro
OHD
LLLP directly measures facepiece leakage. Using state of the art Controlled Negative Pressure, the Quantifit pulls a negative pressure inside your mask, and to keep the pressure constant, it must pull out any additional air that leaks into the respirator. This measurement tells you how much air has leaked into the respirator, and this is converted into a fit factor. Using a challenge pressure of 53.8 – 93.1 L/min, the OHD Quantifit stresses the mask as an employee would while breathing heavily under extreme physical conditions. The manufacturer of the CNP device claims that the use of air as a standard (non-varying) gaseous challenge agent provides a more rigorous test of mask fit than an aerosol agent. If air leaks into a respirator, there is a chance that the particles, vapors, or gas contaminants also may leak in. Using the Redon Protocol, a complete mask fit test can 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 the air is pumped out from the mask at high speed. In this case, a vacuum exists under the mask. The degree of negative pressure depends on the resistance of the filters and on the amount of leaking air. The resistance of the filter is measured with a sealed attachment of the mask to a dummy. This allows the operator to determine the amount of air leaking through the gaps.

Comparison

The main advantage of qualitative fit test methods is the low cost of equipment, while their main drawback is their modest precision, and that they cannot be used to test tight-fitting respirators that are intended for use in atmospheres that exceed 10 PEL (due to the low sensitivity). To reduce the risk of choosing a respirator with poor fit, the mask needs to have a sufficiently high 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 commonly used QLFT was irritant smoke and saccharin, but in 2004, NIOSH advised against using irritant smoke. CNP is a relatively inexpensive and fast method among quantitative methods. However, it is not possible to fit test the disposable filtering face-piece mask (such as the N95, N99, and N100 masks) with CNP. Artificial aerosol fell out of favor due to the need to use an aerosol chamber or a special shelter that supports a given aerosol concentration which makes the test too difficult and costly. 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 introduction of newer instruments, have made all quantitative fit test devices equivalent in price and time required for testing. The CNP method has at present about 15% of the fit test market in industry. One such instrument is the Quantifit. The Current CNC instruments are the PortaCount 8040 and the AccuFIT 9000.

Industry

U.S. law began to require employers to assign and test a mask for each employee prior to assignment to a position requiring the use of a respirator and thereafter every 12 months, and optionally, in case of circumstances that could affect fit (injury, tooth loss, etc.). Other developed countries have similar requirements. A U.S. study showed that this requirement was fulfilled by almost all large enterprises. In small enterprises, with fewer than 10 workers, it was broken by about half of employers in 2001. The main reason for such violations may be the cost of specialized equipment for quantitative fit tests, insufficient accuracy of qualitative fit tests and the fact that small organizations have fewer rigorous compliance processes. + - may be used; - - cannot be used; (*) -

recommended to stop using this method.

References

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External links

Respirator fit testing in YouTube
*Jeff Wee
Be Prepared with a Complete Respiratory Protection Plan
July 2009. Managing Infection Control, 6pp Safety equipment Respirators fr:Masque à gaz#Étanchéité