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Interpreting BLANkET data

​​​​​​The Base Line Air Network of EPA Tasmania (BLANkET) is a network of small air quality stations reporting near real-time indicative particle concentration data (e.g. from smoke or dust) to EPA Tasmania's public web pages. The stations also collect and report meteorological data (air temperature, wind speed, etc.).

What is the purpose of BLANkET?

The purpose is to obtain air quality data in Tasmania away from the major air stations at Hobart, Launceston, Devonport, and George Town. It monitors the spatial extent of smoke events produced by planned burns each autumn, wood smoke produced in winter by domestic heaters, bushfire smoke in summer, and provides a general measure of air quality at other times.

Topics on this page:

​What do you mean by particle concentration data? What are PM10 and PM2.5?

In Tasmania, when we talk of air quality and particles we often mean woodsmoke. The particles in smoke are mostly small, under 1-millionth of a metre in diameter, and are composed of soot (carbon) and complex chemicals such as tars and related compounds. Other sources of particles are airborne dust (generated by both human and natural processes) and other aerosols (such as sea-salt aerosols, and aerosols from vehicle emissions and industrial processes). Particles are often referred to as PM10, meaning all particles with an aerodynamic diameter of up to 10 millionths of a metre, and PM2.5, which are particles up to 2.5 millionths of a metre in aerodynamic diameter. By definition, a measurement of PM10 will include the PM2.5 particles too. BLANkET provides real-time indicative data for PM10 and PM2.5. The smaller particles are potentially the most hazardous to human health, as they can breathed in and can penetrate internal tissue more easily.

Does high PM10 always mean smoke?

No, it doesn't. As noted above, smoke particles are small, and will be included in both the PM10 and PM2.5 measure. If both PM10 and PM2.5 are high, with PM10 only slightly larger than PM2.5, the instrument is probably measuring smoke. If PM10 is high and PM2.5 is low it means there are few very fine particles in the current air sample, and the instrument may therefore be measuring dust or sea salt aerosols.

To check for dust it is worth looking at the meteorological data in the lower panel which shows wind speeds, as high winds can raise dust and keep it airborne. Note that it is possible for dusty air to be carried long distances by strong upper level winds even when surface winds are low, though this is less common in Tasmania than on the mainland of Australia or elsewhere.​

Generally speaking, PM2.5 levels will be high during smoky intervals at a given station. For the reasons given above, PM2.5 is a better indication of smoke than PM10

The About BLANkET​ page has further information about this topic, including an example comparing dust and smoke.

How do I interpret the data plots?

The top panel of the plots shows the air quality data. The PM10 and PM2.5 concentrations are given in micrograms per cubic metre (in short form this is written as µg/m3 or µg m-3 in scientific notation). 

For the current day of data, the most recent measurements are also given in the box to the right of the plot.



As discussed above PM2.5 is a better indicator of smoke than is PM10. PM2.5 is shown as the red triangle symbols in the air quality plots. PM2.5 values below 5 µg m-3 signify very clear air. On a smoky winter's evening in Hobart or Launceston PM2.5 may be near 50 µg m-3 or more for several hours.

The meteorological data plot shows the external (air) temperature, relative humidity, wind speed, wind direction, daily rainfall and barometric pressure.​ If you look carefully you can follow each line. Wind speed is given in kilometres per hour (km/hr, or km hr-1 in scientific notation). Wind direction is given in degrees. Zero degrees is a north wind, 90 degrees is an east wind, 180 degrees is a south wind, and 270 degrees is a west wind. Wind direction is divided by 10 before being plotted, so a wind direction of 18 units on the plot means 180 degrees, or a wind from the south.

For the current day of data the most recent meteorological data are given numerically in the box at the right of the plot.


Key:
T - air temperature

RH - relative humidity
WS - wind speed
WD - wind direction
RF - daily rain fall 
P - mean sea-level pressure (MSLP)

The meteorological data are provided as a guide to interpreting the air quality data. They should not be used in place of Bureau of Meteorology data for determining weather conditions in a given region.​

What is a 'safe' level of smoke?

Detailed information on the health affects of smoke is given on the Tasmanian Department of Health (DoH) website Air Quality page.

The Tasmanian Department of Health provides the following air quality health categories based on the hour-averaged PM2.5 value:​

Good: up to 10 micrograms per cubic metre
Fair: 10 to 25 micrograms per cubic metre;
Poor: 25 to 100 micrograms per cubic metre
​Very poor: over 100 micrograms per cubic metre.

See the Department of Health Track Air Quality page for more information (scroll to the bottom of the page for category information​).

​A summary of health-related information is given here.

A number of health studies carried out both in Australia and overseas have clearly shown there is no 'safe' level of exposure to wood smoke. Any increase in particle levels a given population is exposed to can produce increases in, for example, hospital admissions for respiratory illnesses.

Those most at risk include people with respiratory conditions, the very young, and the elderly, but other people in the wider population can also experience medical problems.

The fine particles found in wood smoke are very difficult to remove from the air. During widespread smoke events it is very difficult for susceptible people to avoid exposure. Standard air conditioning equipment is not able to prevent the small smoke particles from entering domestic buildings.

Further information

For more in-depth information about BLANkET, including its history, national standards and the difference between indicative and reference data, please visit the About BLANkET​ page

​​

Air Specialist
134 Macquarie Street
Hobart TAS 7000
Phone: 03 6165 4599
Email: Enquiries@epa.tas.gov.au

The Environment Protection Authority acknowledges the Tasmanian Aboriginal people as the traditional custodians of lutruwita (Tasmania) and pays respect to their Elders, past and present.