Workplace respirator testing
[2][3] The invention of the first personal sampling pump[4][5] in 1958 made it possible to simultaneously measure the concentrations of air pollution outside and inside a respirator mask.
This picture began to change when it was realized in the 1960s that workers using approved respirators were still being exposed to high levels of harmful contaminants.
In the steel fabrication industry, individuals performing sandblasting wore various types of hoods, usually supplied with air.
In copper smelters, three commonly used types of negative pressure filtering respirators with elastomeric half-masks were examined for their ability to protect workers against concentrations of sulfur dioxide in 1976.
A 1979 study of the effectiveness of self-contained breathing apparatus (SCBA) in protecting firefighters against inhalation of carbon monoxide showed that intermittent usage of these respirators made them ineffective.
US and EU legislation now requires the use of breathing apparatus with the "pressure-demand" mode of air supply (i.e. with positive pressure under the mask during inhalation) for firefighters.
[11] In a study in coal mines, miners frequently removed their respirators in conditions where they perceived the dust level to be low, greatly reducing efficacy.
[13] Factors affecting the level of protection achieved include the snugness of the fit of the respirator to the worker's face,[14] and air movement in the environment.
[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.
Workplace-based testing has led to extensively revised standards for the use of different designs of respirators,[28][29] and has forced manufacturers to pay more attention to methods of hazard reduction such as sealing, ventilation, and automation, and to improvements in technology.
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.
[citation needed] Legislation in industrialized countries establishes limitations on the use of all types of respirators, taking into account the results of field trials of efficacy.
