Local government air quality toolkit: Glossary
A B C D E F G H I J K L M N O P R S T U V W Z
AAQ NEPM, also known as Air NEPM
Ambient Air Quality National Environment Protection Measure.
Absorption
The dissolution of a pollutant in a scrubbing liquid.
Acute (impact)
A health impact that is associated with a short-term exposure to a pollutant.
See also ‘chronic’.
Adsorption
The formation of a layer of foreign substance on an impermeable surface.
AERMET
A data pre-processor used for preparation of meteorological input files for AERMOD.
AERMOD
US Environmental Protection Agency’s recommended steady-state plume dispersion model for near-field regulatory purposes.
Aerodynamic diameter (equivalent aerodynamic diameter)
The ‘size’ of an airborne particle. The ‘aerodynamic diameter’ of a particle of any physical size, shape and density is the diameter of a spherical particle with a density of 1 g/cm3 that behaves the same way in air.
Aerosol
A dispersion of solid or liquid particles in a gas.
Afterburner
Fuel burning equipment, usually a gas burner arrangement, designed for destroying organic vapours and aerosols by combustion before they are released to the atmosphere.
Agricultural burning
The practice of burning the stalks and residue after harvesting of cereal crops, cotton crops and sugar cane, and the burning of cleared timber.
Air impurity
Has the same meaning as in the Protection of the Environment Operations Act 1997 (POEO Act) and includes smoke, dust (including fly ash), cinders, solid particles of any kind, gases, fumes, mists, odours and radioactive substances.
Air pollution
Has the same meaning as in the POEO Act and is the emission into the air of any impurity.
Air quality category (AQC)
Coloured indicators used to summarise air quality measurements. In New South Wales, 5 colour indicators are used to classify air quality as either ‘good’, ‘fair’, ‘poor’, ‘very poor’ or ‘extremely poor’.
Air shed
The geographic region that shares an air mass; the air mass in a region.
Air toxics
Substances generally identified as toxic to humans, often being those materials identified under the National Pollutant Inventory as toxic. They are frequently emitted as colourless vapours or gases, although toxic solid particles are also included. Not to be confused with toxins, which are specifically only toxic compounds formed by biological processes.
Air Toxics NEPM
The National Environment Protection (Air Toxics) Measure aims to improve the information base about ambient air toxics within the Australian environment to facilitate the development of standards.
Ambient air
The external air environment.
Anabatic flow
Movement of warmer air upslope from lower ground.
Appropriate regulatory authority (ARA)
The local or public authority that has designated responsibility for the environmental regulation of premises or activities under the POEO Act.
Atmospheric stability
The property of the atmosphere that determines the extent to which mixing of air and pollutants occurs and hence the effectiveness of dispersion.
Authorised officer
A person appointed by the appropriate regulatory authority under the Protection of the Environment Operations Act 1997 to act on its behalf to deal with environmental problems.
Averaging period
The time over which the concentration of an air pollutant is measured. These are prescribed for the key pollutants and goals in the AAQ NEPM.
Baghouse
The general term for fabric filters and their supporting structure.
Benzene
The fundamental aromatic (cyclic) organic compound, being one of the 5 toxic compounds listed in the Air Toxics NEPM.
Breakthrough
The point at which activated carbon has reached saturation and cannot absorb any further volatile organic compound.
CALINE (CAL3QHCR)
An enhanced version of the CALINE Gaussian dispersion model for predicting air pollution.
CALMET
A meteorological pre-processor for the CALPUFF model.
CALPUFF
A dispersion model that assumes the pollutant behaves like a set of discrete ‘puffs’ of pollutant in the atmosphere.
Carbon monoxide (CO)
The first oxide of carbon, typically a product of incomplete combustion of organic fuels.
Certified Air Quality Professional (CAQP)
An individual certified by the Clean Air Society of Australia and New Zealand to have a specific level of qualifications, skills and experience in air quality practice.
Chronic (impact)
A (health) impact that is severe and associated with long-term exposure to a pollutant (see also ‘Acute’).
Clean Air Regulation
Protection of the Environment Operations (Clean Air) Regulation 2022.
Clean Air Society of Australia and New Zealand (CASANZ)
An organisation that promotes awareness and understanding of air quality issues, with members from a range of sectors with an interest in air quality.
Clean-up notice
A notice to take clean-up action issued under section 91 of the POEO Act.
Climate change
A change in the state of the climate that can be identified by changes in the mean and/or the variability of its properties and persists for an extended period (typically decades or longer). Can be due to natural internal processes or persistent anthropogenic (human) changes.
Collection efficiency
The percentage of air pollutant collected by control equipment.
Compliance
When an operation meets the applicable statutory requirements.
Concentration
A measure of the amount (mass) of a pollutant in a given volume of air, typically expressed in mg/m3 for inside air and µg/m3 for outside air.
For gases, volume ratios can be used in place of concentrations, expressed as parts per million (ppm) or parts per billion (ppb).
Continuous monitoring
A way of monitoring particulate matter and gases in ambient air that provides near real-time measurement of concentration.
Cyclone
An air pollution collection device that collects particulate matter by separating it from a gas stream forced into a vortex within a cylindrical tube.
Density
The amount of mass per unit volume in matter.
Dioxins
The generic name for a large family of cyclic organic chemicals, commonly used to refer loosely to the chlorinated forms of dioxins and furans only. Dioxins of environmental concern contain varying amounts of chlorine and some are toxic to humans (see also ‘Furans’).
Discretionary power
A power granted to a person or public authority acting under the authority of legislation to exercise a measure of personal judgment in relation to the administration of the legislation. For example, determining whether an activity has been carried out in an environmentally unsatisfactory manner under section 95 of the POEO Act, for the purposes of issuing a prevention notice. Such powers are generally subject to merits or judicial review.
Dispersion
The dilution of emissions in the air. Dispersion depends on meteorology, topography, surrounding buildings and emission characteristics.
Dispersion modelling
Use of mathematical and physical principles to quantitatively predict concentrations of pollutants in the environment after release from a source.
Downwash
The downward flow of air on the downwind side of a building or structure.
Drainage flow
Katabatic flow (of cold air) down slopes from higher ground. It is significant in air basins and valleys in light wind conditions, and commonly experienced at night with clear skies.
Dust
Solid particles, either suspended in air or deposited on surfaces; usually referring to coarse, wind-blown particles.
Emission limit
Limit on the amount of pollutant that can be released for activities specified under the POEO Act, the Clean Air Regulation or in conditions attached to an environment protection licence or a consent granted under the EP&A Act.
Enforcement officer
A person belonging to a class of officers or employees prescribed by the regulations in relation to a penalty notice offence who may issue a penalty notice for that offence.
Environment Protection Authority (EPA)
The primary environmental regulator for NSW.
EP&A Act
Environmental Planning and Assessment Act 1979 (NSW).
Exceedance
An instance when the pollutant concentration exceeds the standard or consent condition concentration.
Excessive smoke in relation to a smoke abatement notice
Has the same meaning as in section 135A of the POEO Act for a smoke abatement notice and means ‘the emission of a visible plume of smoke from a chimney for a continuous period of not less than 10 minutes, including a period of not less than 30 seconds when the plume extends at least 10 metres from the point at which the smoke is emitted from the chimney’.
Fabric filter
A device that removes particles from gases by passing them through a filter medium of woven or non-woven (felted) fabric.
Felted fabric (non-woven)
A fabric filter medium consisting of a felted mass of fibres. Felted media are often needle-punched during manufacture to improve bonding of layers.
Filter cake
The compacted particulates that accumulate on a fabric filter, decreasing its filtration capability.
Formaldehyde
One of the 5 toxic compounds listed in the Air Toxics NEPM, it is emitted from some surface adhesives during curing and is also a key intermediate in the formation of photochemical air pollution.
Fugitive emission
Emission of an air pollutant directly into the open air from non-point sources, e.g. wheel-generated dust from haul roads, wind-blown dust from stockpiles.
Fumigation
In meteorology, the sudden mixing back down to ground level of a slowly dispersing pollutant plume trapped in a stable air layer aloft. This occurs when the stable layer, usually formed overnight, breaks up as the lower atmosphere warms during the day.
Furans
The generic name for a large family of cyclic organic chemicals, often grouped with dioxins because of the latter’s similar structure, chemical activity and toxicity. Furans of environmental concern contain varying amounts of chlorine and some are toxic to humans (see also ‘Dioxins’).
GRAL
A dispersion model that predicts ground-level pollutant concentrations by simulating the movement of individual ‘particles’ of a pollutant emitted from an emission sources in a 3-D wind field.
Greenhouse gases
Gases that trap heat in the atmosphere, including carbon dioxide, methane, nitrous oxide and water vapour.
High-volume air sampler (HVAS)
A device for sampling a relatively large volume of air, usually over a 24-hour period on a one day in 6 frequency, through a filter paper to determine gravimetrically the amount of trapped particulate matter. The collected particulate matter may subsequently be analysed for specific substances. Aerodynamically designed inlets can be fitted to high-volume samplers to sample PM10 and PM2.5.
Hygroscopic
Having a tendency to absorb moisture.
Inhalable (fraction of) particles
Particles with an aerodynamic size less than approximately 100 µm that can be inhaled into the nose or throat (see also ‘Thoracic particles’ and ‘Respirable particles’).
Intermittent sampling
Sampling at intervals, either predetermined or random, in contrast to continuous sampling.
Inversion
An atmospheric condition in which the temperature increases (rather than decreases) with height, tending to significantly influence dispersion patterns.
Isokinetic testing
An in-stack technique for measuring either the particulate or aerosol pollutants in the gas stream within a stack or extraction system. The velocity of gas entering the sampling tube must be the same as the velocity of the gas flowing past the tube.
Katabatic flow
Movement downslope of colder air from higher ground. Important in air basins and valleys in light wind conditions, and commonly experienced at night.
Land breeze
Air flow from land to ocean or a lake at night.
LG Act
Local Government Act 1993 (NSW).
Manual gravimetric method
A method for sampling particles by drawing air through a filter and determining the mass by weighing the filters (see also ‘High-volume air sampler’).
Mass
The amount of matter. The metric unit is kilogram (kg). Units commonly used are gram (g), milligram (mg), microgram (µg) and nanogram (ng).
Mechanical collection of particulates
The removal of particles from an air or gas stream using inertial forces to divert the trajectory of the particles from the trajectory of the carrying air or gas stream (see also ‘Cyclone’).
Mechanical shaking
A means of cleaning the filter medium in some types of fabric filters by shaking the bag.
Mercury
One of the ‘heavy metals’ of environmental concern and the only liquid metal at normal temperature. Elemental mercury enters the air during the combustion of fuels in which it is a very volatile impurity.
Micro brewery
A brewery or distillery that produces less than the 30 tonnes of alcohol per day or 10,000 tonnes of alcohol per year threshold set out in the POEO Act Schedule 1, clause 5 ‘Brewing and distilling’.
Micrograms per cubic metre (µg/m3)
A concentration unit commonly used for particulate pollution in ambient air, as measured at STP.
Monitoring network
An array of ambient monitors designed to measure selected air quality aspects for specific purposes. In the context of the Local Government Air Quality Toolkit, there are monitoring networks for the Sydney metropolitan area, the Lower Hunter, Upper Hunter and Illawarra regions, and rural and regional areas, managed by the NSW Department of Climate Change, Energy, the Environment and Water.
Monitoring station
A facility for measuring the concentration of one or more pollutants and meteorological parameters in the ambient air of a region or sub-region.
Monitoring station (performance)
A monitoring station used to measure achievement against an AAQ NEPM goal.
Multi-cyclone
An array of small diameter cyclone collectors arranged to clean large volumes of gases in parallel.
National Environment Protection Council (NEPC)
The national body that makes NEPMs and assesses and reports on their implementation and effectiveness in participating jurisdictions.
National Environment Protection Measures (NEPMs)
A group of measures that set national objectives for protecting or managing aspects of the environment.
National Environment Protection Standard
A quantifiable characteristic of the environment against which environmental quality can be assessed. In the case of air quality, each standard is a pollutant concentration level as measured over a defined averaging period.
National Pollutant Inventory (NPI)
A public online database containing information on the types and quantities of pollutants being emitted from a range of industrial, commercial and transport activities.
Nitrogen dioxide (NO2)
Forms relatively rapidly in air from emitted nitric oxide (NO) and is one of the 6 key air pollutants identified in the AAQ NEPM. It is a brownish, highly reactive gas.
Nitrogen oxides (NOx)
Nitrogen oxides, whether in the nitric oxide (NO) or nitrogen dioxide (NO2) form. They are rapidly converted from one to the other in an atmosphere that is photochemically reactive. NOx is a precursor of photochemical smog measured as ozone.
NTP (different from STP)
Normal temperature and pressure: 20°C and 101.325 kilopascals (kPa).
Odour
A sensation of smell as detected by the olfactory nerve. Intensity of odour is measured in ‘odour units’.
Odour unit (OU)
A measure of odour intensity. The number of odour units in a standard volume of a gas is the number of dilutions with odour-free air needed to bring a sample of odorous gas to the point at which a panel of people just fail to detect the odour.
Opacity (percentage of gas stream)
The percentage of incident light scattered and absorbed by the particles in the gas stream: percentage opacity = 100 – percentage transmittance.
Overspray
Paint, powder or solvent that misses the item being coated. A source of particulate pollution that must be managed in spray painting activities.
Ozone (O3)
A tri-atomic molecular form of oxygen, ozone is a very strong oxidising agent that causes damage to sensitive body tissues, vegetation and materials. It is used as the surrogate for all other products of the photochemical oxidation processes in the formation of ‘smog’ or photochemical air pollution.
Particulate removal efficiency
The efficiency of removal of particles from a gas stream in an air pollution control device.
Particulates
Extremely small solid particles and liquid droplets suspended in the atmosphere (see also ‘PM10’ and ‘PM2.5’).
Penalty notice
A notice issued by an enforcement officer to a person to the effect that the person has committed the offence specified in the notice and requiring the person to pay the prescribed penalty for the offence by the date specified in the notice.
Penalty notice offence
An offence against the POEO Act or the regulations that is prescribed by the regulations as a penalty notice offence.
Permeability
The property of material to allow a liquid or gas to pass through it.
Persistent organic pollutant (POP)
A chemical that remains in the environment for a long time and so becomes widely distributed geographically.
Photochemical smog
The products of hundreds of photochemically catalysed reactions, between the families of VOCs and NOx to produce a mix of oxidant materials, principally ozone, but also including peroxyacylnitrates (PAN) and fine particles or organic materials.
Plume
A trail of air pollution issuing from a source, which may or may not be visible.
PM10
Particulate matter with an equivalent aerodynamic diameter of 10 micrometres (10 µm) or less.
PM2.5
Particulate matter with an equivalent aerodynamic diameter of 2.5 micrometres (2.5 µm) or less.
POEO Act
Protection of the Environment Operations Act 1997 (NSW)
Polychlorinated biphenyls (PCBs)
A family of over 200 synthetic chemicals that were used widely in industry as oils because of their low reactivity and good electrical properties.
Polycyclic aromatic hydrocarbons (PAHs)
These include toxic chemicals and one of them, benzo(a)pyrene, is listed as the marker for PAHs in the Air Toxics NEPM.
Powder coating
A coating that contains no organic solvents and is generally either a thermoplastic or thermosetting powder.
ppb
Parts per billion by volume.
pphm
Parts per hundred million by volume.
ppm
Parts per million by volume.
Pressure drop
The loss in pressure across an air or gas flow device or ducting system. It is particularly important for scrubbers and fabric filters, being a key measure for the operation of air pollution control devices.
Prevention notice
A notice under section 96 of the POEO Act to take action as specified in the notice and by the date specified, to ensure an activity is carried out in an environmentally satisfactory manner, which may include monitoring, sampling or analysing any air pollution, or preparing and carrying out a plan of action to control, prevent or minimise air pollution.
Public register
A publicly accessible register maintained by an appropriate regulatory authority under the POEO Act. A public register lists, among other things, details of environment protection licences and notices issued under the POEO Act, convictions in prosecutions undertaken under the Act, the results of civil proceedings and a summary of conclusions of any mandatory audits undertaken under the Act.
Pulse cleaning
A means of cleaning the filter medium in some types of fabric filters by forcing a short pulse of medium-pressure cleaning air through the bags in the opposite direction to the normal flow.
Rate (of flow or emission)
The amount of pollutant emitted (in a gas stream) per second, usually as the mass per second in kilograms per second, or different units of mass as appropriate.
Rate (of gas flow)
The volume of gas or air flowing past a point in unit time (m3/s).
Residence time
The time a gas or particles remain in some defined space. It can be used to describe the time a gas takes to pass through a piece of control equipment or to remain in a combustion zone. It can also be used to describe how long particulate matter remains suspended in the atmosphere.
Respirable (fraction of) particles
Inhalable particles that can reach the alveoli and be trapped in the lung, having passed the defences of the bronchio-pulmonary system (see also ‘Inhalable particles’ and ‘Thoracic particles’).
Reverse air cleaning
A means of cleaning the filter medium in some types of fabric filters by forcing a flow of cleaning air through the bags in the opposite direction to the normal flow.
Sampling
The process of taking a portion of a material or population for examination or analysis to obtain a representative picture of the whole.
Scheduled activity
An activity listed in Schedule 1 of the POEO Act that requires an environment protection licence and for which the EPA is the appropriate regulatory authority.
Scheduled development work
Work at any premises at which scheduled activities under the POEO Act are not carried on that is designed to enable scheduled activities to be carried on at the premises. It also includes work that is:
- carried on at a premises at which scheduled activities of a class listed in Schedule 1 of the Act are carried on
- designed to enable scheduled activities of a different class in Schedule 1 not authorised by a licence to be carried on at a premises.
Scrubbing
The process of removing pollutants from a gas stream by passing it through a liquid (the ‘scrubbing liquor’).
Sea breeze
Air flow from ocean or a lake to land during the day.
Settling chamber
A simple type of air pollution control device in which particulate pollution is allowed to settle or fall out of an air stream as it passes through the device.
Smog
See ‘Photochemical smog’.
Smoke
Black or grey coloured visible emissions, usually resulting from poor combustion. When white or another colour it indicates the presence of fine particles or aerosol droplets.
Standard (AS, ISO)
A ‘standard’ is a published document that sets out specifications and procedures designed to ensure that a material, product, method or service is fit for its purpose and consistently performs in the way it was intended.
Standards establish a common language that defines quality and establishes safety criteria.
STP (different from NTP)
Standard temperature and pressure: 0°C and 101.325 kilopascals (kPa).
Stratosphere
The layer of the atmosphere immediately above the troposphere. The stratosphere begins about 10 km and ends approximately 50 km above the earth’s surface. The ozone layer is at the top of the stratosphere.
Sulfur dioxide (SO2)
The principal oxide of sulfur resulting from combustion of sulfur bearing fuels.
Sulfur oxides (SOx)
Consisting of sulfur dioxide (SO2) and sulfur trioxide (SO3), but usually expressed as the equivalent SO2.
The Air Pollution Model (TAPM)
A prognostic meteorological model that generates gridded 3-D meteorological data for each of the model run periods.
Thoracic (fraction of) particles
Inhalable particles that pass the larynx (see also ‘Inhalable particles’ and ‘Respirable particles’).
Toluene
Toluene (methyl benzene) is the simplest alkyl substituted aromatic (cyclic) organic compound. It is one of the 5 toxic compounds listed in the Air Toxics NEPM.
Tool for Roadside Air Quality (TRAQ)
An emission estimation tool often used in associated with the CAL3QHCR atmospheric dispersion model.
Total suspended particulates (TSP)
All airborne particles or aerosols less than 100 µm in aerodynamic diameter.
Toxic equivalent (TEQ)
Commonly used in specifying chlorodioxin and furan concentrations, which are converted to a TEQ value based on accepted ratios of toxicity of other members of the family of toxic chlorine-containing compounds to the most toxic member: 2,3,7,8 tetrachlorodibenzo-p-dioxin. Refer to the Clean Air Regulation for the list of accepted ratios.
Transmissometer
An instrument for measuring the opacity of air by measuring the amount of light transmitted through it, using extensive measures to ensure repeatability and reliability of measurement, such as automatic lens cleaning, a controlled frequency light source to eliminate interference and routine automatic calibration. Not to be confused with a ‘smoke meter’.
Troposphere
The lowest layer of the atmosphere extending from the Earth’s surface to about 10 km up, where there is a transition (at the tropopause) to the stratosphere. The troposphere is the most turbulent layer and the location of most meteorological phenomena.
Venturi
A narrow throat in a pipe, where the fluid (gas or liquid) flow is faster. The pressure within the fluid here is lower than in the slower moving fluid in wider sections of the pipe.
Venturi scrubber
A high-energy particulate scrubber.
Volatile organic compound (VOC)
Any organic compound (usually liquid) that readily evaporates at normal temperatures and persists in the air as a vapour. A key precursor to the formation of photochemical smog measured as ozone.
Volume
The space occupied by matter (not to be confused with mass or weight). The metric unit is the cubic metre (m3).
Vortex
A whirling mass of air (or water). Vortices are induced in cyclones to cause the separation of suspended particles from the air stream.
Wet scrubber
An air pollution control device designed for removing particles from gas by capturing the particles on or in liquid (usually water) droplets and separating the droplets from the gas stream.
Woven fabric filter
A fabric filter medium consisting of various styles of woven cloth using natural or synthetic materials.
WRF
The Weather Research and Forecasting Model is an open-source, community developed 3-D numerical meteorological model.
Xylenes
Dimethyl benzenes that are similar to toluene. Xylenes as a total of all isomers are listed in the Air Toxics NEPM.