Workplace respirator testing
The significant differences between real and laboratory-measured effectiveness prompted the National Institute for Occupational Safety and Health (NIOSH) to release two informational messages on respirators in 1982, warning consumers about the unexpectedly low effectiveness of respirators.[19] After extensive discussion, six new definitions of respirator protection factors were agreed upon.[20] For example, the assigned protection factor (APF) of a respirator is the minimum protection factor the respirator must provide under the following circumstances: the respirator will be used by trained and taught workers, after individual selection of masks to fit the face of an employee, and will be used without interruption in the polluted atmosphere.[21] The actual protection experienced by a worker may be significantly lower than this and protection may vary from worker to worker.[22]
Respirator efficacy at Chernobyl
The Chernobyl nuclear accident in 1986 led to an urgent need for protection of workers from radioactive aerosols. Approximately 300,000 negative pressure filtering facepieces of the model "Lepestok" were sent to Chernobyl in June 1986.[23] These respirators were considered to be very effective (the declared protection factor for the most common model was 200). However, the individuals who used these respirators were exposed to excessive contamination. Just as in the case of the studies noted above, the declared protection factor was very different from the actual protection factor under real-world conditions.[24] As seen in other workplace tests, the passage of unfiltered air through the gap between the mask and face undermined the efficiency of the respirator.[25][26][27] However, these discoveries did not lead to a change in assessments of the effectiveness of respirators in the USSR.
Alternatives to respirator use
Workplace-based testing has led to extensively revised standards for the use of different designs of respirators,
Respirators are not convenient; they create discomfort and inhibit communication.[32] The reduction of the field of view due to respirator use leads to an increase in the risk of accidents.[citation needed] Respirators also reinforce overheating at high air temperature.[33] In real-world conditions, these deficiencies often lead to workers removing their respirators periodically, further reducing the efficacy of the respirator. In addition, respirators only protect workers against harmful substances entering the body through the respiratory system, whereas pollutants frequently also enter the body through the skin.[34][35] Respirators thus cannot be used as substitutes for other measures that reduce the impact of air pollution on workers. However, if the respiratory system is the main way that harmful substances enter the body, and if other means of protection do not reduce the impact to an acceptable value, respirators may be a useful supplement. To maximize effectiveness, the type of respirator should be selected for the specific situation, masks should be chosen for employees personally, and workers should be trained to use the respirator effectively.[citation needed]
Reduction in permissible exposure limits
Legislation in industrialized countries establishes limitations on the use of all types of respirators, taking into account the results of field trials of efficacy. The permissible exposure limit [PEL] for several types of respirators was reduced. For example, for negative pressure air-purifying respirators with full face mask and high-efficiency filters, the limits were reduced from 500 PEL to 50 PEL (USA[16]), and from 900 OEL to 40 OEL (UK[33]); for powered air-purifying respirators with a loose-fitting facepiece (hood or helmet), limits were reduced from 1000 PEL to 25 PEL (USA[17]); for powered air-purifying respirators with half mask, limits were reduced from 500 PEL to 50 PEL (USA[16]); for supplied air respirators with full face mask and continuous air supply mode, limits were reduced from 100 OEL to 40 OEL (UK[36]); for self-contained breathing apparatus respirators with air supply on demand, limits were reduced from 100 PEL to 50 PEL (USA). Filtering facepieces and negative pressure half-mask respirators were limited to 10 PEL in the USA.[37]
Respirator type, country | Requirements for protection factor for certification (2013) | Permissible exposure limits prior to workplace testing (year) | Permissible exposure limits after workplace testing (2013) | Minimum values of measured workplace protection factors |
---|---|---|---|---|
PAPR with helmet, USA | > 250 000[6] | up to 1000 PEL | up to 25 PEL[29] | 28, 42 ... |
Negative pressure air-purifying respirator with full face mask, USA | > 250 000[6] | up to 100 PEL (1980) | up to 50 PEL[29] | 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[6] | up to 10 PEL (since the 1960s[29]) | 2.2, 2.8, 4 ... | |
Self-contained breathing apparatus with air supply on demand, USA | > 250 000[6] | up to 1000 PEL (1992) | up to 50 PEL[29] | Monitoring showed low efficiency for carbon monoxide exposure |
The National Institute for Occupational Safety and Health of the USA now requires the manufacturers of high-performance RPE to perform testing at representative workplaces as a requirement for certification.[38]
See also
- Respirator Assigned Protection Factors
- Respirator fit test
References
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