Quality assurance procedures are implemented, both on-the-field and post-data-collection, to ensure that air quality and meteorological parameters measured by the OEH air quality monitoring network are reliable, which is defined as data that is:
- Precise - The data conforms to set guidelines for precision. Precision is tested through daily calibration checks.
- Accurate - The data is accurate. Accuracy is determined by regular multi-point calibration and is dependent on instrument responses remaining linear.
- Representative - The data collected from each site will be consistent with respect to time of day, siting and meteorological conditions.
- Comparable - The data will be comparable to data collected by other institutions using similar collection methods.
Monitoring stations in the air quality monitoring network gather data on gaseous parameters (ozone, sulfur dioxide, carbon monoxide, oxides of nitrogen), fine particles (as PM10 and PM2.5), visibility, wind speed, wind direction, temperature and relative humidity. The instruments that measure these parameters conform to Australian and International Standards.
OEH is accredited by the National Association of Testing Authorities for the operation and maintenance of various air quality instrumentation.
In operating the monitoring program, we use the following measures to ensure that air quality and meteorological parameters our instruments provide are of high quality:
- Siting of instruments – placement of our monitors must meet a clear sky angle of 120°.
- Instrument servicing and maintenance – we perform regular diagnostic tests on key instrument components to detect instrument performance drifts.
- Accuracy of measurements – we perform regular calibration checks for gaseous and particulate air quality monitors and meteorological instruments.
- Logging of issues – any issues affecting instrument performance is documented to ensure anomalous data is identified and managed through data validation.
Data validation procedure
Step 1 – Data is retrieved from instruments onto a data logger and stored on-site in raw data files. The first stage of data validation occurs during data acquisition phase when the data logger invalidates data based on instrument alarms. The raw data files are transmitted on an hourly basis from monitoring sites to a central file server.
Step 2 –A database loading program loads the raw data file into the corporate air quality database according to pre-defined validation and calibration rules, and the data is flagged as production data.
Step 3 – Quality assurance staff reconcile data stored in the production database using various software applications and daily reports. This occurs in consultation with field staff on a daily, weekly and monthly basis.
Step 4 – Irregularities may also be identified by end-users of the data.