Air Quality Monitoring | Calibration Gas Mixtures | Coregas NZ

Air quality monitoring calibration gas mixtures

The measurement of ambient air quality requires highly sensitive analytical instruments which are calibrated with mixtures containing ppm levels of pollutant gases such as CO, NOx and SO2

The most common calibration gas mixture used for outdoor ambient air quality monitoring by the Environment Protection Authorities in Australia is a mixture containing:

50ppm NO, 50ppm SO2 and 0.5% CO in a balance of nitrogen.

The Environment Protection Authorities in some Australian states and territories import this calibration gas mixture from the United States, where the US Environmental Protection Agency verifies its production at several specialty gas filling facilities. Others source it locally from Australian producers such as Coregas. At Coregas we supply this mixture traceable to international standards with ISO/IEC 17025 certification through our NATA accreditation and the use of traceable reference materials to validate our analysis.

In some air quality monitoring applications the concentrations of pollutant gases are measured at such low levels, the instrumentation used will require calibration at lower levels than the mixture cited above. For these applications we can supply ISO/IEC 17025-accredited calibration gas mixtures with reduced concentrations of typical pollutants, such as:

  • 500 ppb SO2 in nitrogen
  • 500 ppm H2S in nitrogen
  • 500 ppb CH4 in nitrogen
  • 500 ppb CO2 in nitrogen
  • 500 ppb propane in nitrogen
  • 500 ppb CO in nitrogen
  • 1 ppm NO in nitrogen
  • 1 ppm NO2 in nitrogen
  • 5 ppm ammonia in nitrogen

As an example of outdoor air quality monitoring parameters in force in Australia, here are the intervention levels valid in the state of Victoria for gaseous pollutant species. The data has been extracted from the Victoria Government Gazette No S 240, December 2001.


SubstanceIntervention level (1 hour average time)
1,3-butadiene0.11 mg/m³
Benzene0.075 mg/m³
Toluene1.88 mg/m³
Xylenes2.08 mg/m³
Formaldehyde0.015 mg/m³
Nitrogen dioxide0.14 ppm
Carbon monoxide29 ppm
PAHs0.0005 mg/m³
Sulphur dioxide0.21 ppm

Benzene, toluene, ethylbenzene and xylene are often collectively studied as BTEX. They are a common group of carcinogens for gas detection in petrochemical refining and refined liquid fuels products storage.

These ISO/IEC 17025-accredited calibration gas mixtures have a measurement uncertainty of 5% relative for the reactive components and 1% relative for the propane, CH4, CO and CO2. The instrumentation used in our laboratory for the above analysis is gas chromatography, FTIR, NDIR or chemiluminescence according to the species to be measured.

If there is a requirement for primary reference materials, we can also produce binary or multi-component calibration gas mixtures according to our NATA ISO 17034 accreditation.

For indoor air quality monitoring, the measurement of formaldehyde is of increasing concern and is being conducted with ever more frequency. Contact our sales team to find out more about this emerging requirement.