Air Quality Glossary

Air Quality Monitoring: The sampling and measuring of ambient (outdoor) air pollutant concentrations.

Attainment Area: An area that is in compliance with the National Ambient Air Quality Standards (NAAQS).

Carbon Monoxide (CO): A regulated air pollutant created from among other things the combustion of fossil fuel.

Criteria Air Pollutants: Pollutants for which there are NAAQS: carbon monoxide, ozone, sulfur dioxide, nitrogen dioxide, particulate matter, and lead.

Emissions & Dispersion Modeling System (EDMS): Computer program established by the Federal Aviation Administration (FAA) to calculate emissions and dispersion of aircraft operations at an airport.

Emissions Inventory: The calculation of total air emissions based on activity levels and emission factors. Results are typically expressed in kilograms per day (kg/day) or tons per year.

Conformity Statement: A regulatory requirement for proposed projects or actions that require federal approval in non-attainment areas that certifies that the proposal conforms with the State Implementation Plan (SIP).

Massachusetts and National Ambient Air Quality Standards (NAAQS): Air pollutant concentrations for defined periods of time (1-hour, 24-hours, annual, etc.) established to protect the public's health and welfare in ambient (outdoor) air.

U. S. Environmental Protection Agency (EPA) computer model to predict fleet-average emissions of carbon monoxide, oxides of nitrogen, and volatile organic compounds from motor vehicles.

Non-Attainment Area: An air quality control region in which EPA has determined that ambient air concentrations exeed the National Ambient Air Quality Standards (NAAQS) for one or more criteria pollutants. The Boston region is designated as a serious non-attainment area for Ozone.

Oxides of Nitrogen: Regulated air pollutants representing different combinations of oxygen and nitrogen. The U. S. EPA has established regulations, including a NAAQS, for nitrogen dioxide (NO2).

Ozone (O3): A regulated air pollutant formed from reactions between VOC and oxides of nitrogen in the presence of sunlight, primarily during summer months. Also generally known as smog.

Particulate Matter (PM10): Regulated particles in the air with a diameter of 10 micron or less. One micron is one-millionth of a meter. Particles with a smaller diameter (PM2.5) are less than 2.5 microns in diameter.

PART5: U. S. EPA model to predict fleet-average emissions of particulate matter (PM10) from motor vehicles

State Implementation Plan (SIP): The Federal Clean Air Act (CAA) requires states with areas that fail to meet the NAAQS to develop a State Implementation Plan (SIP). The SIP describes how the state will reduce and maintain air pollution emissions in order to comply with the federal standards. Key components of a SIP include emission inventories, transportation conformity requirements, control strategies, and attainment demonstration.

Time-In-Mode (TIM): The time an aircraft spends in each mode of the landing and take-off (LTO) cycle.

Vehicle Miles Traveled (VMT): The product of the number of vehicles on a given roadway by the length of the roadway. The units are vehicle miles per year.

Volatile Organic Compounds (VOC): Hydrocarbons associated with motor fuels that are highly reactive and may help form ozone.