Reference Conditions

Section 243 Section 243.107  Reference Conditions All measurements of air quality that are expressed as mass per unit volume (e.g., micrograms per cubic meter, other than for particulate matter (PM 2.5 ) standards contained in Section 243.120(b), (c), and (d) and lead standards contained in Section 243.126(b), are corrected to a reference temperature of 25 °C, and to a reference pressure of 760 millimeters of mercury (1013.2 millibars).  Measurements of PM 2.5 , for purposes of comparison to the standards contained in Section 243.120(b), (c), and (d), and lead, for purposes of comparison to the standards contained in Section 243.126(b), must be reported based upon the actual ambient air volume measured at the actual temperature and pressure at the monitoring site during the measurement period. BOARD NOTE:  Derived from 40 CFR 50.3.