ACO – means Administrative Consent Order. A legal agreement signed by EPA and an individual, business, or other entity through which the violator agrees to pay for correction of violations, take the required corrective or cleanup actions, or refrain from an activity. It describes the actions to be taken, may be subject to a comment period, applies to civil actions, and can be enforced in court.

ACT – means Alternative Control Technique.

Actual emissions – means the rate at which an air contaminant is actually emitted, either directly or indirectly, to the outdoor atmosphere, in units of mass per calendar year, seasonal period, or other time period as specified.

Air contaminant – means any substance, other than water or distillates of air, present in the atmosphere as solid particles, liquid particles, vapors or gases.

Air Pollutant - Any substance in air that could, in high enough concentration, harm man, other animals, vegetation, or material. Pollutants may include almost any natural or artificial composition of airborne matter capable of being airborne. They may be in the form of solid particles, liquid droplets, gases, or in combination thereof. Generally, they fall into two main groups: (1) those emitted directly from identifiable sources and (2) those produced in the air by interaction between two or more primary pollutants, or by reaction with normal atmospheric constituents, with or without photoactivation. Exclusive of pollen, fog, and dust, which are of natural origin, about 100 contaminants have been identified. Air pollutants are often grouped in categories for ease in classification; some of he categories are: solids, sulfur compounds, volatile organic chemicals, particulate matter, nitrogen compounds, oxygen compounds, halogen compounds, radioactive compound, and odors.

Air Pollution - The presence of contaminants or pollutant substances in the air that interfere with human health or welfare, or produce other harmful environmental effects.

ALAPCO – means Association of Local Air Pollution Control Officials. A national association of air pollution control agencies throughout the United States

Allowance – means a tradable unit, which represents the limited authorization to emit one ton of NOx during a control period.

Ambient air quality standard – means a limit on the concentration of an air contaminant in the general outdoor atmosphere as set forth in N.J.A.C. 7:27-13 or 40 CFR 50.

Ammonia (NH3) – means a colorless, pungent gas at standard conditions, having a molecular composition of one nitrogen atom and three hydrogen atoms.

Area Sources - Area sources include emissions from numerous facilities or activities that individually release small amounts of a given pollutant, but collectively they can release significant amounts of a pollutant.  This includes small stationary sources that fall below required emission reporting thresholds by the Emission Statement Program.  Area sources are small and numerous and have emissions which are not readily associated with a single point or a small set of points.  Some of the stationary sources in this sector are sometimes referred to as minor point sources.

Attainment area - A geographic area in which levels of a criteria air pollutant meet the health-based primary standard (national ambient air quality standard, or NAAQS) for the pollutant.  An area may have an acceptable level for one criteria air pollutant, but may have unacceptable levels for others.  Thus, an area could be both attainment and nonattainment at the same time.  Attainment areas are defined using federal pollutant limits set by EPA.