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Sampling and analysis of gases and vapors.
Patty's industrial hygiene, sixth edition: Volume 1 - Hazard recognition. Rose VE, Cohrssen B, eds. Hoboken, NJ: Wiley, 2011 Jan; 1:405-425
Only a few exposure limits for chemicals are couched in terms of a maximum allowable concentration for any given instant because most chemical illnesses occur as a response to a cumulative dose rather than a response to peak exposures. Even in the exceptional cases, some form of time-integrated measurement is usually performed because of the extraordinary resources that would be required to monitor every worker for every moment of their shift. The time period for integration of measurement for toxins with a chronic effect is usually a full work shift, which has traditionally been considered as 8 h (480 min). It was assumed that 5 days of work with exposure at the chronic exposure level were punctuated by a weekend without exposures, and the consequent nightly and weekend recovery periods had been incorporated into pharmacologically based models of metabolism. Today, variations in this work pattern are commonly encountered, and various alternative models have been put forward to account for extended exposures and shorter periods without exposure. Toxins with more acute effects are evaluated on the basis of a shorter exposure period, traditionally 15 min, and the frequency of these short-term exposures and the amount of time between them are also controlled. The standard method for assessing exposures is to measure the toxins in a known volume of air averaged over the appropriate period 8 h or 15 min, or some other appropriate time. Dividing the mass of toxin collected on a sampling device by the volume of air sampled gives a concentration that can be compared to values set as guidelines or regulations for safe working. For extremely acute responses, it may be necessary to establish a ceiling level above which exposures should not occur, and these are monitored by systems with direct readout and often including alarms.
Sampling-equipment; Sampling-methods; Workplace-monitoring; Work-environment; Monitoring-systems; Vapors; Vapor-detectors; Gas-detectors; Gas-meters; Gas-sampling; Gases; Exposure-limits; Exposure-assessment; Biological-monitoring; Industrial-hygiene; Industrial-emissions
Rose VE; Cohrssen B
Patty's industrial hygiene, sixth edition: Volume 1 - Hazard recognition
Page last reviewed: November 6, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division