| 49. | For OELs, concentrations of gases and vapours in air are usually expressed in parts per million (ppm), a measure of concentration by volume, but, may also be expressed in milligrams per cubic metre of air (mg/m³), a measure of concentration by mass. Concentrations of airborne particles (fume, dust, etc.) are usually expressed in mg/m³. In the case of airborne particulates, the limits, where applicable, in Table 2 and Table 3 refer to the inhalable particulate matter, unless specifically indicated as referring to the respirable particulate matter. In the case of man-made mineral fibres, the limit is expressed as fibres per millilitre of air (f/ml). |
