Ambient Air

The air occurring at a particular time and place outside of structures. Often used interchangeably with outdoor air.

Area-wide Sources (also known as "area" sources)

Stationary sources of pollution (e.g., water heaters, gas furnaces, fireplaces, and woodstoves) that are typically associated with homes and non-industrial 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.

Best Available Control Technology/Best Available Control Measure (BACT/BACM)

The most up-to-date methods, systems, techniques, and production processes available to achieve the greatest feasible emission reductions for given regulated air pollutants and processes.

Criteria Pollutants

The 1970 amendments to the Clean Air Act required EPA to set National Ambient Air Quality Standards for certain pollutants known to be hazardous to human health. EPA has identified and set standards to protect human health and welfare for six pollutants; ozone, carbon monoxide, total suspended particulates, sulfur dioxide, lead, and nitrogen oxide. The term, "criteria pollutants" derives from the requirement that EPA must describe the characteristics and potential health and welfare effects of these pollutants.

Emission Inventory

A catalog or listing of emissions from a source, usually based on measurements, calculations, or other information regarding pollutant information.

Federal Clean Air Act (FCAA)

A federal law passed in 1970 and amended in 1977 and 1990 which forms the basis for the national air pollution control effort.

µg/m³

A concentration of an air pollutant (e.g. ozone) is given in micrograms (one-millionth of a gram) per cubic meter air.

Maintenance Area

An area that had previously been designated a nonattainment area, but now meets applicable air quality standards.

Memorandum of Understanding (MOU)

A document describing a bilateral or multilateral agreement between parties. It expresses a convergence of will between the parties, indicating an intended common line of action.

Mobile Sources

Moving objects that release pollution, mobile sources include cars, trucks, buses, planes, trains, motorcycles and gasoline-powered lawn mowers.

Nonattainment

A geographic area that does not meet, or exceeds, established air pollution levels.

Parts per Million (ppm)

A ratio of the amount of one substance to the amount of another, expressed as a unit of solute dissolved in one million units of solution. It denotes the number of units of one substance relative to one million units of another substance.

Primary Standards

National ambient air quality standards designed to protect human health with an adequate margin for safety.

Public Notice

Notification to the public of a pending permit and inviting public comment.

Secondary Standards

National ambient air quality standards designed to protect welfare, including effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate; damage to property, transportation hazards, economic values, and personal comfort and well-being.

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Abbreviations

ADEC

Alaska Department of Environmental Conservation

BACM

best available control measure

BACT

best available control technology

CAA

Clean Air Act

CARB

California Air Resources Board

CFR

Code of Federal Regulations

CNG

compressed natural gas

CO

carbon monoxide

EI

Emissions Inventory

EPA

U.S. Environmental Protection Agency

FIP

Federal Implementation Plan

g/hp-hr

grams per horsepower-hour

GIS

Geographic Information System

g/mi

grams per mile

GVWR

gross vehicle weight rating

HAP

hazardous air pollutant

HC

hydrocarbon

HDD

heavy-duty diesel

HDDV

heavy-duty diesel vehicle

HDV

heavy-duty vehicle

hp

horsepower

km

kilometer

LDT

light-duty truck

LED

low-emission diesel

LEV

low-emission vehicle

LNG

liquefied natural gas

LSG

low-sulfur gasoline

m

meter

MACT

maximum achievable control technology

MPH

miles per hour

MY

model year

NAAQS

National Ambient Air Quality Standards

NOx

nitrogen oxides

O₃

ozone

OBD

onboard diagnostics

OTAQ

the EPA 's Office of Transportation and Air Quality

Pb

lead

PCV

positive crankcase ventilation

PM

particulate matter

PM_2.5

particulate matter smaller than 2.5 microns

PM₁₀

particulate matter smaller than 10 microns

ppb

parts per billion

ppm

parts per million

QA/QC

quality assurance / quality control

RACT

reasonably available control technology

RFG

reformulated gasoline

RPM

revolutions per minute

SCC

source classification code

SIP

State Implementation Plan

SO₂

sulfur dioxide

TCM

transportation control measures

TIP

Transportation Implementation Plan

TPD

tons per day

TPY

tons per year

TSP

total suspended particulate

VID

Vehicle Identification Database

VIN

Vehicle Identification Number

VIR

vehicle inspection report

VMT

vehicle miles traveled

VOC

volatile organic compounds

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