WAC 173-476-180. Reference conditions

(1) All measurements of air quality that are expressed as mass per unit volume µ g/m 3 must be corrected to: (a) A reference temperature of 25°C; and (b) A reference pressure of 760 millimeters of mercury (1,013.2 millibars (hectopascals)). (2) Exception for measurements of PM-2.5 and lead. Measurements of PM-2.5 and lead must be reported based on the actual ambient air volume measured at the actual ambient temperature and pressure at the monitoring site during the measurement period.