Applications
Regulations applicable to the air quality of workplaces
For many hazardous chemicals, it is necessary to protect workers' health by setting pollutant concentration levels in workplace air that must not be exceeded during a reference period, as well as biological limit values. Workplace air quality regulations are often expressed in terms of occupational exposure limits (OELs) or biological limit values (BLVs).
For a given substance, three types of occupational exposure limits may be recommended:
The 8-hour occupational exposure limit (8h-OEL), also known as PEL-TWA (permissible exposure limit - time-weighted average), aims to protect workers' health over the medium and long term, day after day, throughout their working life, from a chemical product. Unless otherwise specified, this is the limit of the time-weighted average concentration of a hazardous substance in the air within a worker's breathing zone over an 8-hour period. A PEL is generally expressed as a time-weighted average (TWA), although some are short-term exposure limits (STELs) or ceilings.
A short-term exposure limit (15 min-STEL) aims to protect workers from adverse health effects (immediate or short-term toxic effects such as irritation) due to exposure peaks. This refers to the limit of the time-weighted average concentration of a chemical product in the worker's breathing zone over a reference period of 15 minutes (unless otherwise specified) during the exposure peak, regardless of its duration.
A ceiling limit or instantaneous OEL is the concentration limit of a chemical product in the worker's breathing zone that must not be exceeded at any time during the work period. This primarily concerns agents known to be highly irritating or corrosive, or capable of causing severe and potentially irreversible effects in a very short time frame.
Exposure limits for hazardous substances in workplace air are a national matter. In different countries, OELs may be legally binding or simply recommendations for a range of substances such as benzene, lead, mercury, crystalline silica, and asbestos. A comparison of workplace air quality standards and recommendations for gaseous and particulate atmospheric pollutants is presented in Table 3 for the United States and Table 4 for Europe and France.
Pollutants | Regulatory limits | Recommended limits | ||
|---|---|---|---|---|
OSHA PEL* | Cal/OSHA PEL** | NIOSH REL*** | ||
\(ppm\) | \(mg/m^3\) | 8-hour TWA (ST) STEL (C) Ceiling | Up to 10-hour TWA (ST) STEL (C) Ceiling | |
Ammonia,\( NH_3\) | 50 | 35 | 25 ppm (ST) 35 ppm | 25 ppm (ST) 35 ppm |
Benzene, \(C_6H_6\) | 1 ppm (ST) 5 ppm | 0.1 ppm (ST) 1 ppm | ||
Carbon Monoxide, \(CO\) | 50 | 55 | 25 ppm (C) 200 ppm | 35 ppm (C) 200 ppm |
Hydrogen Sulfide,\( H_2S\) | ||||
Inorganic Lead (as \(Pb\)) | 0,05 \(mg/m^3\) | 0,05 \(mg/m^3\) | ||
Nitric Oxide, \(NO\) | 25 | 30 | 25 ppm | 25 ppm |
Nitrogen Dioxide, \(NO_2\) | (C) 5 | (C) 9 | (ST) 1 ppm | (ST) 1 ppm |
Ozone, \(O_3\) | 0,1 | 0,2 | 0,1 ppm (ST) 0,3 ppm | (C) 0,1 ppm |
Particulates, PM (not otherwise regulated): Total Dust Respirable Fraction | 15 5 | 10 mg/m3 5 mg/m3 | ||
Sulfur Dioxide, \(SO_2\) | 5 | 13 | 2 ppm (ST) 5 ppm | 2 ppm (ST) 5 ppm |
OSHA PEL*: Permissible Exposure Limits established by the Occupational Safety and Health Administration (OSHA). Cal/OSHA PEL: Permissible Exposure Limits established by the California Division of Occupational Safety and Health (Cal/OSHA). NIOSH REL*: Recommended Exposure Limits by the National Institute for Occupational Safety and Health (NIOSH). (ST): Short-Term Exposure Limit (STEL). (C): Ceiling Limit. | ||||
Pollutants | European Limits – ECHA* | French Limits – INRS** | ||
|---|---|---|---|---|
8-hour OEL \(mg/m^3\) | STEL \(mg/m^3\) | 8-hour OEL \(mg/m^3\) | STEL \(mg/m^3\) | |
Ammonia, \(NH_3\) | 7 | 14 | ||
Benzene,\( C_6H_6\) | 3,25 | 3,25 | ||
Carbon Monoxide, \(CO\) | 23 | 117 | 55 | |
Hydrogen Sulfide,\( H_2S\) | 7 | 14 | 7 | 14 |
Inorganic Lead (as \(Pb\)) | 0,15 | 0,1 | ||
Nitrogen Oxides, \(NO_x\) | 30 | |||
Nitrogen Dioxide, \(NO_2\) | 0,96 | 1,91 | 6 | |
Ozone, \(O_3\) | 0,2 | 0,4 | ||
Particulates , PM (not otherwise regulated): Total Dust Respirable Fraction | 10 5 | |||
Sulfur Dioxide, \(SO_2\) | 5 | 10 | ||
* ECHA: European Chemicals Agency. ** INRS: French National Institute for Research and Safety. STEL: Short-Term Exposure Limit. OEL: Occupational Exposure Limit. | ||||