R 325.2403 Definitions pertaining to contaminants.

Rule 3. As used in these rules: (a) "Maximum allowable concentration" or "MAC" means the threshold limit value or the time-weighted average 8-hour airborne concentration of a contaminant to which a person may be safely exposed. R 325.2413 to R 325.2419, tables 1 to 7, refer to the MAC of a particular contaminant. (b) "Mg/M3" means milligrams of particulate per cubic meter of air. (c) "Mppcf" means millions of particulates per cubic foot of air based on impinger samples counted by light field microscopic techniques. (d) "Non-respirable atmosphere" means an atmosphere which contains insufficient oxygen, or an elevated level of contaminants, which may render a person incapable of self-rescue. (e) "Ppm" means parts of vapor or gas per million parts of air by volume at 25 degrees Celsius and 760 millimeters of mercury pressure. (f) "Source" means a process or equipment which releases a contaminant into the air in concentrations exceeding the MAC.