Odor unit. The amount of odorant(s) in 1 m3 of air detectable by 50 percent of the population
European odor unit is the amount of odorant(s) that, when evaporated into 1 cubic meter of neutral gas at standard conditions, elicits a physiological response from a panel (detection threshold) equivalent to that elicited by 1 European Reference Odor Mass (erom), evaporated in 1 m3 of neutral gas at standard conditions. One erom is equivalent to 123 mg n-butanol (CAS 71-36-3).
Planetary boundary layer
Polymerase chain reaction
Photolytic fragmentation laser-induced fluorescence
Particulate matter having an aerodynamic diameter of 2.5 μm or less.
Particulate matter having an aerodynamic diameter of 10 μm or less.
Permit nutrient plan
“[A]ny discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel,…concentrated animal feeding operation,…from which pollutants are or may be discharged. This term does not include agricultural stormwater discharges and return flows from irrigated agriculture” (33 USC § 1362(14)).
Parts per billion (by volume)
Pounds per day
Parts per million (by volume)
The degree of agreement between two or more results on the same property of identical test material expressed as the repeatability or reproducibility of an instrument reading the results.
Particle size distribution
Prevention of significant deterioration
Pounds per square inch
Relaxed eddy accumulation
Rolling herd average
Reactive organic gase
State air pollution regulatory agency
Sulfur chemiluminescence detector
Sulfur hexafluoride (used as an atmospheric tracer)