Workplace respirator testing: Difference between revisions
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{{short description|Testing of respirators in real life conditions}} |
{{short description|Testing of respirators in real life conditions}} |
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[[File:Workplace Protection Factors Measurements.jpg|thumb|Workplace Protection Factors Measurements|thumb|300px|Example of measurement of efficiency of the respirator (in the workplace). Description: (1) Personal sampling pump, (2) The cassette and the filter for determining the concentration (in the breathing zone), (3) The cassette and the filter to determine the concentration (under a mask), (4) The sampling line (from the breathing zone), and (5) The sampling line (from the mask).]] |
[[File:Workplace Protection Factors Measurements.jpg|thumb|Workplace Protection Factors Measurements|thumb|300px|Example of measurement of efficiency of the respirator (in the workplace). Description: (1) Personal sampling pump, (2) The cassette and the filter for determining the concentration (in the breathing zone), (3) The cassette and the filter to determine the concentration (under a mask), (4) The sampling line (from the breathing zone), and (5) The sampling line (from the mask).]] |
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To protect [[Workforce|workers]] from air contaminants, employers often utilized [[respirator]]s in the workplace. Protection of workers' life and health required that the effectiveness of the respirator must be consistent with the degree of air pollution. The respiratory protective equipment (RPE) or devices (RPD) has different designs, and their protective properties differ markedly. If |
To protect [[Workforce|workers]] from air contaminants, employers often utilized [[respirator]]s in the workplace. Protection of workers' life and health required that the effectiveness of the respirator must be consistent with the degree of air pollution. The respiratory protective equipment (RPE) or devices (RPD) has different designs, and their protective properties differ markedly. If employers wished to select the appropriate device, he or she would need to know in advance what [[Respirator Assigned Protection Factors|level of protection it would provide]]. |
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Initially, the effectiveness of respirators |
Initially, the effectiveness of respirators was evaluated with tests in the laboratories. Unfortunately, workers who properly used and maintained even approved respirators (with [[HEPA|high-efficiency filters]]), were still presenting with excessive exposure of harmful agents. This finding prompted experts to adjust their original opinions.<ref name="Patty-19852"><cite class="citation book">Cralley, Lesly; Cralley, Lester (1985). "..". ''Patty's Industrial Hygiene and Toxicology''. '''3A''' (2 ed.). New York: Willey-Interscience. pp. 677–678. {{ISBN|0 471-86137-5}}.</cite><templatestyles src="Module:Citation/CS1/styles.css"></templatestyles></ref> |
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In the late 1960s, researchers found that true effectiveness of respirators in the workplaces was significantly lower than during the tests in [[Laboratory|laboratories]]. |
In the late 1960s, researchers found that the true effectiveness of respirators in the workplaces was significantly lower than during the tests in [[Laboratory|laboratories]]. Therefore, since the 1970s, specialists started RPD tests in workplaces within industrialized countries. Specialists have begun to use the results of workplace testing for developing regulations to govern the selection RPD.<ref name="NIOSH-02"><cite class="citation book">Miller, Donald; et al. (1987). [https://www.cdc.gov/niosh/docs/87-108/ ''NIOSH Respirator Decision Logic'']. DHHS (NIOSH) Publication No. 87-108. National Institute for Occupational Safety and Health. p. 61. [[Digital object identifier|doi]]:[[doi:10.26616/NIOSHPUB87108|10.26616/NIOSHPUB87108]]<span class="reference-accessdate">. Retrieved <span class="nowrap">16 July</span> 2016</span>.</cite></ref> The goal is safe, the allowable use of all RPD designs.<ref name="Обзор-20142"><cite class="citation journal">Kirillov, Vladimir; et al. (2014). [http://en.toxreview.ru/magazine/?c4a=20140600 "Overview of Industrial Testing Outcome of Respiratory Organs Personal Protection Equipment"]. ''Toxicological Review'' (in English and Russian). '''6''' (129): 44–49. [[Digital object identifier|doi]]:[[doi:10.17686/sced rusnauka 2014-1034|10.17686/sced_rusnauka_2014-1034]]. [[International Standard Serial Number|ISSN]] [//www.worldcat.org/issn/0869-7922 0869-7922].</cite></ref> |
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== Background == |
== Background == |
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[[File:Respirator Certification - As Vital as the Air We Breathe.webm|thumb|A video describing respirator certification]] |
[[File:Respirator Certification - As Vital as the Air We Breathe.webm|thumb|A video describing respirator certification]] |
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The invention of the first personal sampling pump<ref name="Шервуд-1966" /><ref name="Шервуд-1960" /> (1958) made it possible to simultaneously measure the concentrations of air pollutions outside the respirator mask, and at the same time - pollution of inhaled air (under a facepiece). Comparison of these measurement results |
The invention of the first personal sampling pump<ref name="Шервуд-1966" /><ref name="Шервуд-1960" /> (1958) made it possible to simultaneously measure the concentrations of air pollutions outside the respirator mask, and at the same time - pollution of inhaled air (under a facepiece). Comparison of these measurement results shows the effectiveness of respiratory protective equipment. But until the 1970s experts mistakenly believed that the protective properties of the respirator under laboratory and in the production conditions are not significantly different. Measuring the effectiveness of respirators under production conditions were not performed; limits of areas of safe use for different types of respirators were established on the basis of laboratory tests only. |
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But the results of the first workplace studies have shown that the effectiveness of respirators all designs - is very fickle, and strongly depend on the correctness of their use (continuous use in polluted atmosphere, etc...), and on the leakage of contaminated air under the mask through the gaps between it and the worker's face. It was found that respirators' efficiency in the workplaces were much lower, as compared to laboratory conditions. This has led to |
But the results of the first workplace studies have shown that the effectiveness of respirators all designs - is very fickle, and strongly depend on the correctness of their use (continuous use in polluted atmosphere, etc...), and on the leakage of contaminated air under the mask through the gaps between it and the worker's face. It was found that respirators' efficiency in the workplaces were much lower, as compared to laboratory conditions. This has led to revising the boundaries of the application of RPE different designs and prompted to develop requirements for the organization of their application, fixing them in the national legislation.<ref name="Стандарт-1997" /><ref name="Стандарт-США-OSHA" /> The results of measurements forced to pay more attention to the [[Hierarchy of hazard control|technical methods of protection]] (sealing, [[Ventilation (architecture)|ventilation]], [[automation]], changing [[technology]], and others.). |
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If the facepiece of the respirator is tightly-fitted (elastomeric quarter or half masks, filtering facepieces, or full-face masks), efficiency decreases due to leakage of unfiltered air through the gaps between the mask and face. These gaps are formed because employees must perform a variety of movements under production circumstances that testers in the lab do not. Even properly fitted masks may slip sometimes. |
If the facepiece of the respirator is tightly-fitted (elastomeric quarter or half masks, filtering facepieces, or full-face masks), efficiency decreases due to leakage of unfiltered air through the gaps between the mask and face. These gaps are formed because employees must perform a variety of movements under production circumstances that testers in the lab do not. Even properly fitted masks may slip sometimes. |
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=== The initial stage ''(1970s - 1980s)'' === |
=== The initial stage ''(1970s - 1980s)'' === |
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(1974)<ref name="П1-1974" /> The researchers studied the effectiveness of respirators used by [[miner]]s. Scientists simultaneously measured dust concentrations with the personal samplers and two dust collectors - without mask and in the facepiece. Also, they measured the proportion of time |
(1974)<ref name="П1-1974" /> The researchers studied the effectiveness of respirators used by [[miner]]s. Scientists simultaneously measured dust concentrations with the personal samplers and two dust collectors - without the mask and in the facepiece. Also, they measured the proportion of time; then the respirators were used by miners. For this purpose, two [[thermistor|thermistors]] (one in the facepiece, the other on the belt) were used; over-heating PTC with expired air was a sign of wearing a mask. Because the convenience of the respirators affect the timeliness of its usage, scientists have studied the opinion of the miners on the use of respirators. A detailed report was published before the publication of the article.<ref name="П1-1974-0" /> |
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(1974)<ref name="П2-1974" /> The study found that respirators can be a good addition to |
(1974)<ref name="П2-1974" /> The study found that respirators can be a good addition to effective dedusting [[Ventilation (architecture)|ventilation]]. The authors recommended to carry out [[Physical examination|medical examination]] of workers - in [[employment]] and periodically. |
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(1975)<ref name="П-1975" /> Experts measured the concentration of [[dust]] under respiratory protective devices of workers-[[Abrasive blasting|sandblasters]], and outside - but not simultaneously. The measurement results showed that exposure to air pollution on employees exceeds the [[Permissible exposure limit|permissible value]] |
(1975)<ref name="П-1975" /> Experts measured the concentration of [[dust]] under respiratory protective devices of workers-[[Abrasive blasting|sandblasters]], and outside - but not simultaneously. The measurement results showed that exposure to air pollution on employees exceeds the [[Permissible exposure limit|permissible value]] and that the supply of clean air into the hood reduces adverse effects. Also, measurements have shown that there may be excessive exposure to workers during breaks (when the respirator may be withdrawn); and discovered the fault of some respirators. Authors recommended: to organize the correct application of RPD, to reduce the concentration of dust in the air, and apply the abrasive material with lower [[Quartz|silica]] content. |
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(1976)<ref name="П-1976" /> The concentrations of [[sulfur dioxide]] were measured under the negative pressure filtering respirator with elastomeric half |
(1976)<ref name="П-1976" /> The concentrations of [[sulfur dioxide]] were measured under the negative pressure filtering respirator with an elastomeric half-mask, and in the breathing zone (simultaneously); and the results were used to calculate the respiratory protection factors PF (such as the concentration ratio, ambient to in-facepiece). Experts analyzed the results of only those measurements, during which the masks were not removed. They found a positive relationship between a comfortableness of respirators, and their effectiveness, as the workers tightened the straps of the harness at the convenient masks much stronger. |
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(1979)<ref name="СО-1979" /> Efficiency of [[ |
(1979)<ref name="СО-1979" /> Efficiency of [[self-contained breathing apparatus]] (SCBA) [[Mine Safety Appliances|MSA]] has been studied when they were used by [[firefighter]]s. This SCBA had had an air supply into the mask with "on-demand" mode (with negative pressure under the mask during [[inhalation]]). Evaluation of the effectiveness of the respirator was conducted by determining the content of [[carboxyhemoglobin]] in the [[blood]] immediately after the cessation of fire extinguishing. [[Carboxyhemoglobin]] formed due to inhalation of [[carbon monoxide]]. The [[biomonitoring]] results showed: (1) the intermittent usage of these respirators makes it totally ineffective; (2) even in continuous usage of such breathing apparatus does not provide effective protection. The results of this study (and other similar studies) led to restricting the use of respirators with fresh air supply "on-demand"; and to prohibit their use in fighting fires. US and EU legislation obliges to use only self-contained breathing apparatus with "pressure-demand" mode of air supply (it provide positive pressure under the mask during inhalation) in extinguishing fires. |
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(1980)<ref name="П1-1980" /> Evaluating the effectiveness of RPE was performed with [[biomonitoring]]. Researchers measured a [[styrene]] concentration in the expired air and in the [[urine]]. Since the [[Absorption (skin)|absorption]] of styrene through skin was small, respirators were able to provide reliable protection of workers. |
(1980)<ref name="П1-1980" /> Evaluating the effectiveness of RPE was performed with [[biomonitoring]]. Researchers measured a [[styrene]] concentration in the expired air and in the [[urine]]. Since the [[Absorption (skin)|absorption]] of styrene through the skin was small, respirators were able to provide reliable protection of workers. |
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(1980)<ref name="П2-1980" /> This study clearly showed that using respirators result (exposure to harmful substances on workers) is highly dependent on the organization of their application, and on training of the workers: |
(1980)<ref name="П2-1980" /> This study clearly showed that using respirators result (exposure to harmful substances on workers) is highly dependent on the organization of their application, and on the training of the workers: |
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Employees use a respirator several times. The average protection factor of the respirator in one of the workers (who always used a respirator in a timely and accurately), proved to be 26 times greater than that of all other workers. |
Employees use a respirator several times. The average protection factor of the respirator in one of the workers (who always used a respirator in a timely and accurately), proved to be 26 times greater than that of all other workers. |
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The authors have raised the question of the need to describe the effectiveness of the respirator using different terms. One term - for cases of timely application of the respirator, and the other - for use with interruptions (for description the real protection of employees). |
The authors have raised the question of the need to describe the effectiveness of the respirator using different terms. One term - for cases of timely application of the respirator, and the other - for use with interruptions (for description the real protection of employees). |
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(1983)<ref name="П1-1983" /> Employees used a respirator with forced air supply to the facepiece; expected protection factor = 1000 (and more). But measured protection factors were considerably lower: 4.5 - 62 times. This disparity has prompted experts to conduct additional research to discover the causes of |
(1983)<ref name="П1-1983" /> Employees used a respirator with forced air supply to the facepiece; expected protection factor = 1000 (and more). But measured protection factors were considerably lower: 4.5 - 62 times. This disparity has prompted experts to conduct additional research to discover the causes of differences.<ref name="П2-1983" /> |
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(1983)<ref name="П2-1983" /> Employees used a respirator ([[Powered air-purifying respirator|PAPR]]): air flow 184 l/min, the degree of air purification with filters 99.97%. But they are often discovered climbing of its face shield, and the minimum protection factors reaches 1.1, 1.2 ... . Some of respirators do not provide a snug fit to the face of the faces. Measurement results showed that the rest in the room with |
(1983)<ref name="П2-1983" /> Employees used a respirator ([[Powered air-purifying respirator|PAPR]]): air flow 184 l/min, the degree of air purification with filters 99.97%. But they are often discovered climbing of its face shield, and the minimum protection factors reaches 1.1, 1.2 ... . Some of the respirators do not provide a snug fit to the face of the faces. Measurement results showed that the rest in the room with clean air greatly reduces the impact of air pollution on the workers and that respirators alone can not reliably protect them. It was also found that the calculation of the protective factors may give different results for different chemicals (for the same measurement carried out). |
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(1984)<ref name="П1-1984" /> Measured respirators' protection factors were very unstable. Scientists have proposed to establish the boundaries of the safe use of respirators based on the results obtained not in the laboratories, but in the workplaces, under application without interruption. This principle, with some variations, is used in developed countries today. Experts proposed to establish the [[Respirator Assigned Protection Factors|expected protection factors]] so that the real effectiveness was greater than the expected effectiveness with a probability of 90% and in 95% of cases. The authors analyzed the results |
(1984)<ref name="П1-1984" /> Measured respirators' protection factors were very unstable. Scientists have proposed to establish the boundaries of the safe use of respirators based on the results obtained not in the laboratories, but in the workplaces, under application without interruption. This principle, with some variations, is used in developed countries today. Experts proposed to establish the [[Respirator Assigned Protection Factors|expected protection factors]] so that the real effectiveness was greater than the expected effectiveness with a probability of 90% and in 95% of cases. The authors analyzed the results and offered to reduce the permissible usage limits of the half-mask respirators with forced air supply ([[Powered air-purifying respirator|PAPR]]) from 500 to 50 PEL. |
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(1984)<ref name="П2-1984" /> Experts have studied the effectiveness of half |
(1984)<ref name="П2-1984" /> Experts have studied the effectiveness of half-mask respirators, used by employees with and without a beard under the exposure of coarse dust. The hair on the faces of the staff did not lead to a decrease in the effectiveness of respirators. This result can be explained by the fact that the dust was large, and it passes through the gap only partially. All Western manuals require workers shave face when using respirators with tight-fitting facepieces. |
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[[File:Коэффициенты защиты PAPR en.jpg|thumb|400px|Protection Factors of [[Powered air-purifying respirator|Powered Air-Purifying Respirator (PAPR)]] with loose-fitting facepiece (hood or helmet).<ref name="П3-1984" /><ref name="П3-1986" /> Result: Assigned PF was lowered from 1000 to 25 PEL (USA) |
[[File:Коэффициенты защиты PAPR en.jpg|thumb|400px|Protection Factors of [[Powered air-purifying respirator|Powered Air-Purifying Respirator (PAPR)]] with loose-fitting facepiece (hood or helmet).<ref name="П3-1984" /><ref name="П3-1986" /> Result: Assigned PF was lowered from 1000 to 25 PEL (USA), and for 40 OEL (UK)]] |
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(1984)<ref name="П3-1984" /> This study was the third study (<ref name="П2-1983" /><ref name="П1-1984" />), which showed low |
(1984)<ref name="П3-1984" /> This study was the third study (<ref name="П2-1983" /><ref name="П1-1984" />), which showed low-efficiency respirators ([[Powered air-purifying respirator|Powered air-purifying respirator with a loose-fitting facepiece, hood or helmet]]), which consistently provides reliable protection in the laboratory (PF>1000). The minimum protection factor of respirators applied continuously, were as follows: for the 3M model - 28, and for the Racal model - 42. |
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A significant difference between the real and laboratory efficiency prompted the [[National Institute for Occupational Safety and Health]] (NIOSH) released in 1982 two informational messages on respirators, warning consumers about the low effectiveness of RPD of the type that is expected to provide reliable protection.<ref name="NIOSH-1987" /> The experts were alarmed: they do not understand why (after the supplying more than 115 liters of clean air per minute under the facepiece) there are a lot of pollution in the inhaled air. |
A significant difference between the real and laboratory efficiency prompted the [[National Institute for Occupational Safety and Health]] (NIOSH) released in 1982 two informational messages on respirators, warning consumers about the low effectiveness of RPD of the type that is expected to provide reliable protection.<ref name="NIOSH-1987" /> The experts were alarmed: they do not understand why (after the supplying more than 115 liters of clean air per minute under the facepiece) there are a lot of pollution in the inhaled air. |
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* The results of these investigations led to a decrease of the [[Respirator Assigned Protection Factors|expected (assigned) protection factor (APF)]] of such respirators 40-fold, from 1000 to 25 (US). The authors said that the study of one of the tested respirator models in the [[wind tunnel]] |
* The results of these investigations led to a decrease of the [[Respirator Assigned Protection Factors|expected (assigned) protection factor (APF)]] of such respirators 40-fold, from 1000 to 25 (US). The authors said that the study of one of the tested respirator models in the [[wind tunnel]] had been found reduction of the protection factor up to 17 at an air speed of 2 m/s airflow in certain directions.<ref name="Cecala-1981" /> |
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This study showed that laboratory tests |
This study showed that laboratory tests could not be used as a reliable indicator of the effectiveness of respiratory protective equipment. Authors are encouraged to use the results of measurements of respirators' protection factors in the workplaces (with continuous use) to develop reasonable restrictions for different types of respiratory protective equipment. |
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* Research efficiency in the workplace led to |
* Research efficiency in the workplace led to developing special terminology to describe the effectiveness of respirators adequately. |
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Public discussion of the proposed terms |
Public discussion of the proposed terms was carried out in 1982-1986.<ref name="ПП-1982" /><ref name="ПП-1983-1" /><ref name="ПП-1983-2" /><ref name="ПП-1985" /> As a result of this discussion, the experts gave definitions for the six respirator protection factors that can be measured in different conditions in the workplaces and in the laboratories. |
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These definitions began to be used officially,<ref name="NIOSH-0" /> as well as in the preparation of articles about the trials of respirators.<ref name="ПП-1986" /> |
These definitions began to be used officially,<ref name="NIOSH-0" /> as well as in the preparation of articles about the trials of respirators.<ref name="ПП-1986" /> |
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For example, the assigned protection factor (APF), is the minimum PF, which RPD (of this type) must ensure if: the respirator will be used by trained and taught workers, after [[Respirator fit test|individual selection masks to face an employee]]; if it is to be used without interruption in the polluted atmosphere - in most cases (but not in all cases). |
For example, the assigned protection factor (APF), is the minimum PF, which RPD (of this type) must ensure if: the respirator will be used by trained and taught workers, after [[Respirator fit test|individual selection masks to face an employee]]; if it is to be used without interruption in the polluted atmosphere - in most cases (but not in all cases). |
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The experts recommended to |
The experts recommended to developing APF values based on measurements of the protective factors in the workplace, or in considering the values of APF of similar respirators' types. |
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* They found that if the protection factors are not stable, the average efficiency is strongly dependent on smaller values:<ref name="ПП-1997" /> If the same worker used respirator twice, and if the protection factor was 230,000 in the first case, and the protection factor was 19 in the second (example values from<ref name="П-2003" />), the average protection factor was only 38. (Penetrations in the first and second cases are 5.26% and 0%, respectively; and the average penetration is equal to 2.63%). Medium PF is strongly dependent on the minimum values. |
* They found that if the protection factors are not stable, the average efficiency is strongly dependent on smaller values:<ref name="ПП-1997" /> If the same worker used respirator twice, and if the protection factor was 230,000 in the first case, and the protection factor was 19 in the second (example values from<ref name="П-2003" />), the average protection factor was only 38. (Penetrations in the first and second cases are 5.26% and 0%, respectively; and the average penetration is equal to 2.63%). Medium PF is strongly dependent on the minimum values. |
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=== Effectiveness in coal mining === |
=== Effectiveness in coal mining === |
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The authors have shown that the average decrease dustiness of inhaled air in [[Coal mining in the United Kingdom|coal mining in the UK]] due to the use of respirators is 41% (1.7 times).<ref name="RP-1981" /> Low |
The authors have shown that the average decrease dustiness of inhaled air in [[Coal mining in the United Kingdom|coal mining in the UK]] due to the use of respirators is 41% (1.7 times).<ref name="RP-1981" /> Low-efficiency respirators due to the fact that the miners used respirators intermittently or not used at all (in the conditions of effective [[Ventilation (architecture)|ventilation]] and low dust concentration). They can not determine when the dust concentration is more than acceptable, and when it is necessary to use a respirator. |
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The handbook<ref name="Handbook2003" /> discusses the results of measurements of respirators' performance. The dust concentration was reduced by 92% with the use of half |
The handbook<ref name="Handbook2003" /> discusses the results of measurements of respirators' performance. The dust concentration was reduced by 92% with the use of half-mask respirators while working [[Longwall mining|longwall shearer]]; decreased three times (on average). Helmet with forced filtering air supply ([[Powered air-purifying respirator|PAPR]]) reduces the concentration of dust in half. The expected decrease in dust concentration of the two types of respirators are 10 and 25 respectively. In subsequent publications of [[Centers for Disease Control and Prevention|CDC]] (on the subject of reducing the dust content in underground mining) RPE are not mentioned at all. |
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[[File:Лепесток-200 старая распорка - 2.jpg|thumb|150px|right|Filtering half-mask [[w:ru:Респираторы ШБ «Лепесток»|Lepestok]], view from the inner side of the semi-finished product. The effectiveness of this filtering facepiece was overestimated by orders of magnitude - without justification; for the period 1956 to 2015 the industry produced over 6 billion of respirators.]] |
[[File:Лепесток-200 старая распорка - 2.jpg|thumb|150px|right|Filtering half-mask [[w:ru:Респираторы ШБ «Лепесток»|Lepestok]], view from the inner side of the semi-finished product. The effectiveness of this filtering facepiece was overestimated by orders of magnitude - without justification; for the period 1956 to 2015, the industry produced over 6 billion of respirators.]] |
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===Use in the Chernobyl accident === |
===Use in the Chernobyl accident === |
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[[File:Médaille Tchernobyl goutte de sang.jpg|thumb|150px|The central detail of the [[Chernobyl liquidators|Liquidators']] medal, with traces of alpha (α) and beta (β) particles and gamma (γ) rays over a drop of blood.]] |
[[File:Médaille Tchernobyl goutte de sang.jpg|thumb|150px|The central detail of the [[Chernobyl liquidators|Liquidators']] medal, with traces of alpha (α) and beta (β) particles and gamma (γ) rays over a drop of blood.]] |
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Liquidation of consequences of the [[Chernobyl disaster|Chernobyl accident]] required the reliable protection of people from radioactive aerosols. Even a small amount of [[Radioactive contamination|radioactive substances]] can seriously harm human health if it enters into their bodies<ref name="Городинский-1979" /> (because of the small distance from the tissues). |
Liquidation of consequences of the [[Chernobyl disaster|Chernobyl accident]] required the reliable protection of people from radioactive aerosols. Even a small amount of [[Radioactive contamination|radioactive substances]] can seriously harm human health if it enters into their bodies<ref name="Городинский-1979" /> (because of the small distance from the tissues). |
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Aerosol particles deposited in the lungs |
Aerosol particles deposited in the lungs can remain there for many years, and it increases the risk of diseases. Eliminating the consequences of the accident were carried out the best experts, including members of the [[Kurchatov Institute]]. Only one of the manufacturers RPD sent to Chernobyl approximately 300,000 negative pressure filtering facepieces model "Lepestok" only in June 1986.<ref name="Лепесток-2015" /> These respirators are considered to be very effective (the declared protection factor of 200 for most common model "Lepestok-200"). |
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But the application of this model on a large scale has revealed numerous cases of excessive exposure to air pollution on people. This has led experts to question the high efficiency of the respirator, and it is similar to the events in the US nuclear industry in the late 1960s.<ref name="Patty-1985" /> Doubts were strong; |
But the application of this model on a large scale has revealed numerous cases of excessive exposure to air pollution on people. This has led experts to question the high efficiency of the respirator, and it is similar to the events in the US nuclear industry in the late 1960s.<ref name="Patty-1985" /> Doubts were strong; they are forced to carry out an independent study of the effectiveness in a foreign laboratory.<ref name=Hoover-2001 /> Specialists conducted parallel attempts to identify the reasons for the low efficiency of the respirator in Chernobyl.<ref name="Огородников-2006" /> |
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The results of research in Chernobyl and in the United States were similar: the filter material is well caught a fine aerosol,<ref name="Конференция-1990-2" /> and created a small resistance to the passage of air through it; but a lot of unfiltered air passes through the gap between the mask and face. Research has shown that one can expect the minimum values of the protection factor 2÷8,<ref name="Конференция-1990-1" /> or even 1.5.<ref name=Hoover-2001 /> |
The results of research in Chernobyl and in the United States were similar: the filter material is well caught a fine aerosol,<ref name="Конференция-1990-2" /> and created a small resistance to the passage of air through it; but a lot of unfiltered air passes through the gap between the mask and face. Research has shown that one can expect the minimum values of the protection factor 2÷8,<ref name="Конференция-1990-1" /> or even 1.5.<ref name=Hoover-2001 /> |
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Representatives of the institution in which the model of respirator was developed, given their very original interpretation of the results of independent (foreign) tests: |
Representatives of the institution in which the model of the respirator was developed, given their very original interpretation of the results of independent (foreign) tests: |
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<blockquote>... in 20% of cases the protection factor (fit factor) exceeded the declared value (200). ... Consequently, the respirator model provides the declared efficiency.</blockquote>. |
<blockquote>... in 20% of cases, the protection factor (fit factor) exceeded the declared value (200). ... Consequently, the respirator model provides the declared efficiency.</blockquote>. |
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In addition, the respirator designers stated that experts from Kurchatov Institute conducted their measurements "illiterate".<ref name="Огородников-2006" /> |
In addition, the respirator designers stated that experts from Kurchatov Institute conducted their measurements "illiterate".<ref name="Огородников-2006" /> |
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== Analysis of performance == |
== Analysis of performance == |
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Field measurement results showed that the respirators are the most recent and the [[Hierarchy of hazard control|most unreliable means of protection]]. |
Field measurement results showed that the respirators are the most recent and the [[Hierarchy of hazard control|most unreliable means of protection]]. |
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The effectiveness of respiratory protective equipment is unstable and unpredictable. Respirators cannot substitute other measures, that reduce the impact of air pollution on the staff (sealing equipment, ventilation and so on), but only supplement them. Respirators are not convenient |
The effectiveness of respiratory protective equipment is unstable and unpredictable. Respirators cannot substitute other measures, that reduce the impact of air pollution on the staff (sealing equipment, ventilation and so on), but only supplement them. Respirators are not convenient; they create [[Comfort|discomfort]] and [[irritation]] and prevent [[communication#Verbal communication|communication]].<ref name="П1-2007" /> The reduction of the [[field of view]] leads to an increase in the risk of [[accident]]s. |
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RPE reinforce overheating at |
RPE reinforce overheating at high air temperature.<ref name="П1-2002" /> These and other deficiencies often prevent the use of respirators in the polluted atmosphere without interruptions. But if the RPD is not used, it becomes useless. |
||
Workers using respirators partially lose performance. Industrial hygienists know many cases where harmful substances enter the body not through the respiratory system, but in other ways (through skin<ref name="П2-2007" />). Even the timely use of a respirator may not be sufficient for reliable protection of workers.<ref name="П2-1993" /> |
Workers using respirators partially lose performance. Industrial hygienists know many cases where harmful substances enter the body not through the respiratory system, but in other ways (through the skin<ref name="П2-2007" />). Even the timely use of a respirator may not be sufficient for reliable protection of workers.<ref name="П2-1993" /> |
||
If the respiratory system is the main way of receipt of harmful substances in the body, and if the use of other means of protection does not allow to reduce the impact to an acceptable value, employee must use respirators. They should be selected taking into account their effectiveness (it depends on the respirator type); masks should be chosen for employees personally |
If the respiratory system is the main way of receipt of harmful substances in the body, and if the use of other means of protection does not allow to reduce the impact to an acceptable value, the employee must use respirators. They should be selected taking into account their effectiveness (it depends on the respirator type); masks should be chosen for employees personally, and workers should be learned, and trained - in accordance with legal requirements. This reduces the risk of occupational diseases as much as possible. |
||
== Measurements == |
== Measurements == |
||
Comparison of the results of tests of various types of respirators in the laboratories and in the workplaces showed that laboratory tests do not allow to properly assess the real effectiveness of respirators (even if they are applied without interruption). Therefore, legislation in industrialized countries establishes limitations on the use of all types of respirators, taking into account such differences, and taking into account the results of field trials. This field measurements revealed low efficiency of several types of respirators, and forced more strictly limit their use: for negative pressure air-purifying respirators with full face mask and high |
Comparison of the results of tests of various types of respirators in the laboratories and in the workplaces showed that laboratory tests do not allow to properly assess the real effectiveness of respirators (even if they are applied without interruption). Therefore, legislation in industrialized countries establishes limitations on the use of all types of respirators, taking into account such differences, and taking into account the results of field trials. This field measurements revealed low efficiency of several types of respirators, and forced more strictly limit their use: for negative pressure air-purifying respirators with full face mask and high-efficiency filters - from 500 PEL to 50 PEL (USA<ref name="П1-1984" />), from 900 OEL to 40 OEL (UK<ref name="П1-2002" />); |
||
for Powered Air-Purifying Respirators with loose-fitting facepiece (hood or helmet) — from 1000 PEL to 25 PEL (USA<ref name="П3-1984" />), PAPR with half mask — from 500 PEL to 50 PEL (USA<ref name="П1-1984" />), for supplied Air Respirators with full face mask and continuous air supply mode - from 100 OEL to 40 OEL (UK<ref name="П2-2002" />); for SCBA and SAR with air supply on |
for Powered Air-Purifying Respirators with a loose-fitting facepiece (hood or helmet) — from 1000 PEL to 25 PEL (USA<ref name="П3-1984" />), PAPR with half mask — from 500 PEL to 50 PEL (USA<ref name="П1-1984" />), for supplied Air Respirators with full face mask and continuous air supply mode - from 100 OEL to 40 OEL (UK<ref name="П2-2002" />); for SCBA and SAR with air supply on-demand mode — from 100 PEL to 50 PEL (USA). |
||
The results of numerous field tests and analysis |
The results of numerous field tests and analysis led to the restriction of application limits of filtering facepieces and negative pressure half-mask respirators to 10 PEL in US.<ref name="NIOSH-2004" /> |
||
{| class="wikitable" style="text-align:center" |
{| class="wikitable" style="text-align:center" |
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Revision as of 20:06, 28 November 2019
 | This article may require copy editing for grammar, style, cohesion, tone, or spelling. (June 2019) |
To protect workers from air contaminants, employers often utilized respirators in the workplace. Protection of workers' life and health required that the effectiveness of the respirator must be consistent with the degree of air pollution. The respiratory protective equipment (RPE) or devices (RPD) has different designs, and their protective properties differ markedly. If employers wished to select the appropriate device, he or she would need to know in advance what level of protection it would provide.
Initially, the effectiveness of respirators was evaluated with tests in the laboratories. Unfortunately, workers who properly used and maintained even approved respirators (with high-efficiency filters), were still presenting with excessive exposure of harmful agents. This finding prompted experts to adjust their original opinions.[1]
In the late 1960s, researchers found that the true effectiveness of respirators in the workplaces was significantly lower than during the tests in laboratories. Therefore, since the 1970s, specialists started RPD tests in workplaces within industrialized countries. Specialists have begun to use the results of workplace testing for developing regulations to govern the selection RPD.[2] The goal is safe, the allowable use of all RPD designs.[3]
Background
The invention of the first personal sampling pump[4][5] (1958) made it possible to simultaneously measure the concentrations of air pollutions outside the respirator mask, and at the same time - pollution of inhaled air (under a facepiece). Comparison of these measurement results shows the effectiveness of respiratory protective equipment. But until the 1970s experts mistakenly believed that the protective properties of the respirator under laboratory and in the production conditions are not significantly different. Measuring the effectiveness of respirators under production conditions were not performed; limits of areas of safe use for different types of respirators were established on the basis of laboratory tests only.
But the results of the first workplace studies have shown that the effectiveness of respirators all designs - is very fickle, and strongly depend on the correctness of their use (continuous use in polluted atmosphere, etc...), and on the leakage of contaminated air under the mask through the gaps between it and the worker's face. It was found that respirators' efficiency in the workplaces were much lower, as compared to laboratory conditions. This has led to revising the boundaries of the application of RPE different designs and prompted to develop requirements for the organization of their application, fixing them in the national legislation.[6][7] The results of measurements forced to pay more attention to the technical methods of protection (sealing, ventilation, automation, changing technology, and others.).
If the facepiece of the respirator is tightly-fitted (elastomeric quarter or half masks, filtering facepieces, or full-face masks), efficiency decreases due to leakage of unfiltered air through the gaps between the mask and face. These gaps are formed because employees must perform a variety of movements under production circumstances that testers in the lab do not. Even properly fitted masks may slip sometimes.
If the respirator facepiece is loosely fitted, polluted air can also enter the breathing zone due to its injection (with moving stream of ambient air, unless it is motionless). But there are no significant drafts in the laboratory during RPD approval tests.
A small number of testers can not simulate all the variety of shapes and sizes of faces, and a 20-minute certification lab test[8] cannot simulate all the variety of movements performed in workplaces. In addition, testers are more careful about putting on and using their masks than workers more broadly.
Published research
The initial stage (1970s - 1980s)
(1974)[9] The researchers studied the effectiveness of respirators used by miners. Scientists simultaneously measured dust concentrations with the personal samplers and two dust collectors - without the mask and in the facepiece. Also, they measured the proportion of time; then the respirators were used by miners. For this purpose, two thermistors (one in the facepiece, the other on the belt) were used; over-heating PTC with expired air was a sign of wearing a mask. Because the convenience of the respirators affect the timeliness of its usage, scientists have studied the opinion of the miners on the use of respirators. A detailed report was published before the publication of the article.[10]
(1974)[11] The study found that respirators can be a good addition to effective dedusting ventilation. The authors recommended to carry out medical examination of workers - in employment and periodically.
(1975)[12] Experts measured the concentration of dust under respiratory protective devices of workers-sandblasters, and outside - but not simultaneously. The measurement results showed that exposure to air pollution on employees exceeds the permissible value and that the supply of clean air into the hood reduces adverse effects. Also, measurements have shown that there may be excessive exposure to workers during breaks (when the respirator may be withdrawn); and discovered the fault of some respirators. Authors recommended: to organize the correct application of RPD, to reduce the concentration of dust in the air, and apply the abrasive material with lower silica content.
(1976)[13] The concentrations of sulfur dioxide were measured under the negative pressure filtering respirator with an elastomeric half-mask, and in the breathing zone (simultaneously); and the results were used to calculate the respiratory protection factors PF (such as the concentration ratio, ambient to in-facepiece). Experts analyzed the results of only those measurements, during which the masks were not removed. They found a positive relationship between a comfortableness of respirators, and their effectiveness, as the workers tightened the straps of the harness at the convenient masks much stronger.
(1979)[14] Efficiency of self-contained breathing apparatus (SCBA) MSA has been studied when they were used by firefighters. This SCBA had had an air supply into the mask with "on-demand" mode (with negative pressure under the mask during inhalation). Evaluation of the effectiveness of the respirator was conducted by determining the content of carboxyhemoglobin in the blood immediately after the cessation of fire extinguishing. Carboxyhemoglobin formed due to inhalation of carbon monoxide. The biomonitoring results showed: (1) the intermittent usage of these respirators makes it totally ineffective; (2) even in continuous usage of such breathing apparatus does not provide effective protection. The results of this study (and other similar studies) led to restricting the use of respirators with fresh air supply "on-demand"; and to prohibit their use in fighting fires. US and EU legislation obliges to use only self-contained breathing apparatus with "pressure-demand" mode of air supply (it provide positive pressure under the mask during inhalation) in extinguishing fires.
(1980)[15] Evaluating the effectiveness of RPE was performed with biomonitoring. Researchers measured a styrene concentration in the expired air and in the urine. Since the absorption of styrene through the skin was small, respirators were able to provide reliable protection of workers.
(1980)[16] This study clearly showed that using respirators result (exposure to harmful substances on workers) is highly dependent on the organization of their application, and on the training of the workers: Employees use a respirator several times. The average protection factor of the respirator in one of the workers (who always used a respirator in a timely and accurately), proved to be 26 times greater than that of all other workers. The authors have raised the question of the need to describe the effectiveness of the respirator using different terms. One term - for cases of timely application of the respirator, and the other - for use with interruptions (for description the real protection of employees).
(1983)[17] Employees used a respirator with forced air supply to the facepiece; expected protection factor = 1000 (and more). But measured protection factors were considerably lower: 4.5 - 62 times. This disparity has prompted experts to conduct additional research to discover the causes of differences.[18]
(1983)[18] Employees used a respirator (PAPR): air flow 184 l/min, the degree of air purification with filters 99.97%. But they are often discovered climbing of its face shield, and the minimum protection factors reaches 1.1, 1.2 ... . Some of the respirators do not provide a snug fit to the face of the faces. Measurement results showed that the rest in the room with clean air greatly reduces the impact of air pollution on the workers and that respirators alone can not reliably protect them. It was also found that the calculation of the protective factors may give different results for different chemicals (for the same measurement carried out).
(1984)[19] Measured respirators' protection factors were very unstable. Scientists have proposed to establish the boundaries of the safe use of respirators based on the results obtained not in the laboratories, but in the workplaces, under application without interruption. This principle, with some variations, is used in developed countries today. Experts proposed to establish the expected protection factors so that the real effectiveness was greater than the expected effectiveness with a probability of 90% and in 95% of cases. The authors analyzed the results and offered to reduce the permissible usage limits of the half-mask respirators with forced air supply (PAPR) from 500 to 50 PEL.
(1984)[20] Experts have studied the effectiveness of half-mask respirators, used by employees with and without a beard under the exposure of coarse dust. The hair on the faces of the staff did not lead to a decrease in the effectiveness of respirators. This result can be explained by the fact that the dust was large, and it passes through the gap only partially. All Western manuals require workers shave face when using respirators with tight-fitting facepieces.
(1984)[21] This study was the third study ([18][19]), which showed low-efficiency respirators (Powered air-purifying respirator with a loose-fitting facepiece, hood or helmet), which consistently provides reliable protection in the laboratory (PF>1000). The minimum protection factor of respirators applied continuously, were as follows: for the 3M model - 28, and for the Racal model - 42.
A significant difference between the real and laboratory efficiency prompted the National Institute for Occupational Safety and Health (NIOSH) released in 1982 two informational messages on respirators, warning consumers about the low effectiveness of RPD of the type that is expected to provide reliable protection.[23] The experts were alarmed: they do not understand why (after the supplying more than 115 liters of clean air per minute under the facepiece) there are a lot of pollution in the inhaled air.
- The results of these investigations led to a decrease of the expected (assigned) protection factor (APF) of such respirators 40-fold, from 1000 to 25 (US). The authors said that the study of one of the tested respirator models in the wind tunnel had been found reduction of the protection factor up to 17 at an air speed of 2 m/s airflow in certain directions.[24]
This study showed that laboratory tests could not be used as a reliable indicator of the effectiveness of respiratory protective equipment. Authors are encouraged to use the results of measurements of respirators' protection factors in the workplaces (with continuous use) to develop reasonable restrictions for different types of respiratory protective equipment.
- Research efficiency in the workplace led to developing special terminology to describe the effectiveness of respirators adequately.
Public discussion of the proposed terms was carried out in 1982-1986.[25][26][27][28] As a result of this discussion, the experts gave definitions for the six respirator protection factors that can be measured in different conditions in the workplaces and in the laboratories. These definitions began to be used officially,[29] as well as in the preparation of articles about the trials of respirators.[30]
For example, the assigned protection factor (APF), is the minimum PF, which RPD (of this type) must ensure if: the respirator will be used by trained and taught workers, after individual selection masks to face an employee; if it is to be used without interruption in the polluted atmosphere - in most cases (but not in all cases). The experts recommended to developing APF values based on measurements of the protective factors in the workplace, or in considering the values of APF of similar respirators' types.
- They found that if the protection factors are not stable, the average efficiency is strongly dependent on smaller values:[31] If the same worker used respirator twice, and if the protection factor was 230,000 in the first case, and the protection factor was 19 in the second (example values from[32]), the average protection factor was only 38. (Penetrations in the first and second cases are 5.26% and 0%, respectively; and the average penetration is equal to 2.63%). Medium PF is strongly dependent on the minimum values.
Other workers[32] also meet very strong volatility of efficiency (for example, the protection factor of 51 000 and 13 for the same worker).
The initial stage of research yielded the following results: experts developed a common terminology to describe the protective properties of the respirators; a methodology for measuring protection factors in different conditions of respirators' usage in the workplaces and laboratories; and the realization that national legislation should set limits for the use of all types of respirators based on their performance, measured not in the laboratory, but in the workplaces. The first studies also clearly confirmed that the use of respirators is the most unreliable method of protecting workers from all known methods. Therefore, respirators should be used only when other methods can not be used; or when other methods can not reduce the exposure of air pollution on people to an acceptable safe level.
Since the effectiveness of respirators may vary depending on different circumstances related to the organization of their application, the RPE should be used as part of a respiratory protection program (a complex of measures aimed at eliminating the causes which may reduce the effectiveness of respiratory protection).
Effectiveness in coal mining
The authors have shown that the average decrease dustiness of inhaled air in coal mining in the UK due to the use of respirators is 41% (1.7 times).[33] Low-efficiency respirators due to the fact that the miners used respirators intermittently or not used at all (in the conditions of effective ventilation and low dust concentration). They can not determine when the dust concentration is more than acceptable, and when it is necessary to use a respirator.
The handbook[34] discusses the results of measurements of respirators' performance. The dust concentration was reduced by 92% with the use of half-mask respirators while working longwall shearer; decreased three times (on average). Helmet with forced filtering air supply (PAPR) reduces the concentration of dust in half. The expected decrease in dust concentration of the two types of respirators are 10 and 25 respectively. In subsequent publications of CDC (on the subject of reducing the dust content in underground mining) RPE are not mentioned at all.
Use in the Chernobyl accident
Liquidation of consequences of the Chernobyl accident required the reliable protection of people from radioactive aerosols. Even a small amount of radioactive substances can seriously harm human health if it enters into their bodies[35] (because of the small distance from the tissues). Aerosol particles deposited in the lungs can remain there for many years, and it increases the risk of diseases. Eliminating the consequences of the accident were carried out the best experts, including members of the Kurchatov Institute. Only one of the manufacturers RPD sent to Chernobyl approximately 300,000 negative pressure filtering facepieces model "Lepestok" only in June 1986.[36] These respirators are considered to be very effective (the declared protection factor of 200 for most common model "Lepestok-200").
But the application of this model on a large scale has revealed numerous cases of excessive exposure to air pollution on people. This has led experts to question the high efficiency of the respirator, and it is similar to the events in the US nuclear industry in the late 1960s.[37] Doubts were strong; they are forced to carry out an independent study of the effectiveness in a foreign laboratory.[38] Specialists conducted parallel attempts to identify the reasons for the low efficiency of the respirator in Chernobyl.[39]
The results of research in Chernobyl and in the United States were similar: the filter material is well caught a fine aerosol,[40] and created a small resistance to the passage of air through it; but a lot of unfiltered air passes through the gap between the mask and face. Research has shown that one can expect the minimum values of the protection factor 2÷8,[41] or even 1.5.[38]
Representatives of the institution in which the model of the respirator was developed, given their very original interpretation of the results of independent (foreign) tests:
... in 20% of cases, the protection factor (fit factor) exceeded the declared value (200). ... Consequently, the respirator model provides the declared efficiency.
.
In addition, the respirator designers stated that experts from Kurchatov Institute conducted their measurements "illiterate".[39]
Many cases of excessive exposure to air pollution during operation at the Chernobyl plant did not lead to a change in assessments of the effectiveness of respirators - as happened in the United States before.
Analysis of performance
Field measurement results showed that the respirators are the most recent and the most unreliable means of protection. The effectiveness of respiratory protective equipment is unstable and unpredictable. Respirators cannot substitute other measures, that reduce the impact of air pollution on the staff (sealing equipment, ventilation and so on), but only supplement them. Respirators are not convenient; they create discomfort and irritation and prevent communication.[42] The reduction of the field of view leads to an increase in the risk of accidents.
RPE reinforce overheating at high air temperature.[43] These and other deficiencies often prevent the use of respirators in the polluted atmosphere without interruptions. But if the RPD is not used, it becomes useless.
Workers using respirators partially lose performance. Industrial hygienists know many cases where harmful substances enter the body not through the respiratory system, but in other ways (through the skin[44]). Even the timely use of a respirator may not be sufficient for reliable protection of workers.[45]
If the respiratory system is the main way of receipt of harmful substances in the body, and if the use of other means of protection does not allow to reduce the impact to an acceptable value, the employee must use respirators. They should be selected taking into account their effectiveness (it depends on the respirator type); masks should be chosen for employees personally, and workers should be learned, and trained - in accordance with legal requirements. This reduces the risk of occupational diseases as much as possible.
Measurements
Comparison of the results of tests of various types of respirators in the laboratories and in the workplaces showed that laboratory tests do not allow to properly assess the real effectiveness of respirators (even if they are applied without interruption). Therefore, legislation in industrialized countries establishes limitations on the use of all types of respirators, taking into account such differences, and taking into account the results of field trials. This field measurements revealed low efficiency of several types of respirators, and forced more strictly limit their use: for negative pressure air-purifying respirators with full face mask and high-efficiency filters - from 500 PEL to 50 PEL (USA[19]), from 900 OEL to 40 OEL (UK[43]); for Powered Air-Purifying Respirators with a loose-fitting facepiece (hood or helmet) — from 1000 PEL to 25 PEL (USA[21]), PAPR with half mask — from 500 PEL to 50 PEL (USA[19]), for supplied Air Respirators with full face mask and continuous air supply mode - from 100 OEL to 40 OEL (UK[46]); for SCBA and SAR with air supply on-demand mode — from 100 PEL to 50 PEL (USA).
The results of numerous field tests and analysis led to the restriction of application limits of filtering facepieces and negative pressure half-mask respirators to 10 PEL in US.[47]
| RPD type, country | Requirements for the protection factor for certification (2013) | Limitations prior the workplace testing (year) | Limitations after the workplace testing (2013) | The minimum values of the measured workplace protection factors |
|---|---|---|---|---|
| PAPR with helmet, USA | > 250 000[8] | up to 1000 PEL | up to 25 PEL[7] | 28, 42 ... |
| Negative pressure air-purifying respirator with full face mask, USA | > 250 000[8] | up to 100 PEL (1980) | up to 50 PEL[7] | 11, 16, 17 ... |
| Negative pressure air-purifying respirator with full face mask, UK | > 2000 (for gases) or >1000 (for aerosols) | up to 900 OEL (1980) | up to 40 OEL | |
| Negative pressure air-purifying respirator with half mask facepiece, USA | > 25 000[8] | up to 10 PEL (since the 1960s[7]) | 2.2, 2.8, 4 ... | |
| Self-contained breathing apparatus with air supply on demand, USA | > 250 000[8] | up to 1000 PEL (1992) | up to 50 PEL[7] | (monitoring showed a low efficiency under the carbon monoxide exposure) |
The significant difference between the real and laboratory efficiency prompted the National Institute for Occupational Safety and Health to require the manufacturers of high-performance RPE perform its testing at the adequate workplaces (as a requirement for respirator certification in the United States[48]).
Due to the fact that respirators wearing cannot provide a reliable protection, National Institute for Occupational Safety and Health has developed a guide to reduce the dust concentration: in the underground coal mines;[49] in the other mines;[50] and other similar documents with specific recommendations.
See also
References
- ^ Cralley, Lesly; Cralley, Lester (1985). "..". Patty's Industrial Hygiene and Toxicology. 3A (2 ed.). New York: Willey-Interscience. pp. 677–678. ISBN 0 471-86137-5.
- ^ Miller, Donald; et al. (1987). NIOSH Respirator Decision Logic. DHHS (NIOSH) Publication No. 87-108. National Institute for Occupational Safety and Health. p. 61. doi:10.26616/NIOSHPUB87108. Retrieved 16 July 2016.
- ^ Kirillov, Vladimir; et al. (2014). "Overview of Industrial Testing Outcome of Respiratory Organs Personal Protection Equipment". Toxicological Review (in English and Russian). 6 (129): 44–49. doi:10.17686/sced_rusnauka_2014-1034. ISSN 0869-7922.
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- ^ Technical Committee PH/4, Respiratory protection, ed. (1997). British Standard BS 4275:1997 "Guide to implementing an effective respiratory protective device programme" (3 ed.). 389 Chiswick High Road, London: British Standards Institution. ISBN 0-580-28915 X.
{{cite book}}: CS1 maint: location (link) CS1 maint: numeric names: editors list (link) - ^ a b c d e OSHA standard 29 CFR 1910.134 "Respiratory Protection"
- ^ a b c d e NIOSH standard 42 Code of Federal Register Part 84 "Respiratory Protective Devices"
- ^ Harris, H.E.; DeSieghardt, W.C.; Burgess, W. A.; Reist, Parker (1974). "Respirator Usage and Effectiveness in Bituminous Coal Mining Operations". American Industrial Hygiene Association Journal. 35 (3): 159–164. doi:10.1080/0002889748507018. ISSN 1542-8117. Retrieved 10 July 2016.
- ^ Harris, H.E.; DeSieghard, W.C. (1973). Respiratory Protection and Respirable Dust in Underground Coal Mines (PDF). Everett, Massachusetts: ACS Division of Energy & Fuel - Preprints. pp. 165–179.
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- ^ Smith, Thomas; Ferrel, Willard; Varner, Michael; Putnam, Robert (1980). "Inhalation exposure of cadmium workers: effects of respirator usage". American Industrial Hygiene Association Journal. 41 (9): 624–629. doi:10.1080/15298668091425400. ISSN 1542-8117. Retrieved 10 July 2016.
- ^ Myers, Warren; Peach, M.J. III (1983). "Performance measurements on a powered air-purifying respirator made during actual field use in a silica bagging operation". The Annals of Occupational Hygiene. 27 (3): 251–259. doi:10.1093/annhyg/27.3.251. ISSN 0003-4878. Retrieved 10 July 2016.
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- ^ Fergin, Stanley (1984). "Respirator Evaluation for Carbon Setters with Beards". American Industrial Hygiene Association Journal. 45 (8): 533–537. doi:10.1080/15298668491400223. ISSN 1542-8117. PMID 6475760. Retrieved 10 July 2016.
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- ^ Myers, Warren; Peach III, Michael; Cutright, Ken; Iskander, Wafik (1986). "Field Test of Powered Air-Purifying Respirators at a Battery Manufacturing Facility". Journal of the International Society for Respiratory Protection. 4 (1): 62–89. ISSN 0892-6298.
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- ^ Cecala, Andrew B.; Volkwein, Jon C.; Thomas, Edward D.; Charles W. Urban (1981). Protection Factors of the Airstream Helmet. Bureau of Mines Report No. 8591. p. 10.
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{{cite journal}}: CS1 maint: DOI inactive as of August 2019 (link) - ^ Chang, Fu-Kuei; Chen, Mei-Lien; Cheng, Shu-Fang; Shih, Tung-Sheng; Mao, I-Fang (2007). "Evaluation of dermal absorption and protective effectiveness of respirators for xylene in spray painters". International Archives of Occupational and Environmental Health. 81 (2): 145–150. doi:10.1007/s00420-007-0197-9. ISSN 0340-0131. PMID 17492305. Retrieved 16 July 2016.
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{{cite journal}}: CS1 maint: DOI inactive as of August 2019 (link) - ^ Bollinger, Nancy; Campbell, Donald; Coffey, Christopher (2004). "III. Respirator Selection Logic Sequence". NIOSH Respirator Selection Logic. DHHS (NIOSH) Publication No. 2005-100. NIOSH Respirator Policy Group; Heinz Ahlers, Roland BerryAnn, Frank Hearl, Richard Metzler, Teresa Seitz, Douglas Trout and Ralph Zumwalde. Cincinnati, OH: The National Institute for Occupational Safety and Health (NIOSH). pp. 3–16.
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