Ambient air	The surrounding air
Area-based source	Any source of air pollution that is released over a small area but which cannot be classified as a ‘point source’ in emissions inventory
Best Management Practice	Methods that are considered to be the most effective and practical in terms of preventing or reducing pollution from non-point sources
Biogenic emissions	Emissions from natural sources including vegetation and soil
Biosphere	The part of the planet and its atmosphere that can support life
Characterisation	The determination of the composition and properties of a product, emission, effluent or solid waste
Criteria	Descriptive factors taken into account by EPAs in establishing standards for various pollutants; used to determine allowable concentration levels
Dynamic olfactometer	An apparatus that delivers a flow of mixtures of odorous and neutral gases with known dilution ratios. Used in human panels assessing odours. Olfactometry is the measurement of the response of assessors to olfactory stimuli
Emissions	Substances released to the environment
Emissions factor	The relationship between the amount of pollution produced and the amount of raw material processed
Emissions inventory	A database of the volume of emissions released to air, measured over time. Emissions inventory can be compared with air pollutant levels in an area to determine if emissions are reducing air quality
Environmental transport	The movement through the biosphere of a substance (e.g. chemical) including the physical, biological, and chemical interactions undergone by the substance
Ethanol	Alternative fuel for motor vehicles derived from grain and corn
Fossil fuels	Fuels derived from fossilised organic matter such as coal, oil and petroleum.
Fugitive emissions	Substances which escape to air from a source not associated with a specific process but scattered throughout the plant, e.g. leaks from equipment, dust from stockpiles
Guideline	Suggested values for maximum concentrations or emissions of a substance for the protection of environment and human health. See Standards
Ground level concentrations	Measured or estimated concentrations (using fisherperson modelling) of a pollutant at ground level
Hedonic tone	The appreciation of smell; varies from person to person.
Industry concentration	An average concentration calculated from results for industry sourced pollution over a one year period; the concentration at any time could be higher or lower than the annual average.
Inventory	A detailed, complete list.
Inversion (temperature)	A layer of warm air which prevents the rising of cooling air and therefore traps pollutants beneath it. It is the inverse of what normally occurs where temperature decreases with increasing altitude. If there is no wind and the temperature during the day is not sufficiently high to restore the normal thermal gradient, the inversion can persist and intensify causing an air pollution episode.
Mobile source	Anything that moves and pollutes the air, e.g. cars, lawn mowers, airplanes.
NPI National Pollution Inventory (Australia)	Collects and provides information on type and amount of pollutants emitted to the environment in Australia. Data is gathered from industry and non-industry sources.
National Environment Protection Council (Australia). NEPC	Makes National Environmental Protection Measures and assesses and reports on their implementation.
NEPM	National Environment Protection Measure (Australia)
Odour nuisance	Odour leading to complaints.
Parameter	A variable, measurable property whose value is a determinant of the characteristics of a system, e.g. temperature, pressure and density are parameters of atmosphere.
Photochemical reactions	Chemical reactions which occur in the presence of ultra-violet and visible light
Photochemical smog	Air pollution formed in the presence of ultra-violet or visible light from the sun
Plume	A visible or measurable discharge of a contaminant from a point source, e.g. a plume of smoke
Point source	A confined, stationary conveyance from which pollutants are discharged, e.g. stack, pipe, tunnel and well
PM10	Particulate matter that is less than 20 micrometres in diameter, also known as respirable particles
Pollutant	A chemical which may reduce the quality of the environment. Pollution is the presence of one or more pollutants in the environment
Real-time monitoring	Monitoring and measuring system that provides automated up-to-the minute information to enable prompt decision making
Runoff	Water from melting snow, rainfall or irrigation that flows across ground surface and eventually is returned to streams, carrying with it pollutants
Secondary pollutant	Formed by chemical reactions between pollutants discharged to the environment and naturally occurring substances, e.g. ground level ozone is formed by the reaction between nitrogen, hydrocarbons and oxygen
Sensitive receptor	Typically includes residential dwellings, schools, medical centres, public parks and gardens and places of commerce
Source of emissions	An activity or process which can lead to the release of a pollutant
Standard	Level of pollutants prescribed by law that cannot be exceeded. Legally enforceable