Melbourne Bush Fire Smoke Haze

Air conditioning and closed windows are not a catch all solution to bushfire smoke

Smoke dust and its potentially carcinogenic contaminants, such as formaldehyde and benzene, are known to affect health on both a long and short-term basis.

The small size of smoke particulates (PM0.7 to PM1.5 microns) and vapours found in air testing can easily pass through standard air conditioning filters.

As an example, CETEC’s research in early 2020 showed that Premium Grade Buildings, as defined by the Property Council of Australia’s ‘Guide to Office Building Quality', reduce the amount of hazardous bushfire smoke contaminants inhaled by their occupants by 90%.

But what about the rest of us?

Is it better to stay in the office than work from home?

Environmentally, we normally worry about PM2.5 or particles that range up to 2.5 microns in size.  This is reported daily in the Air Quality Index (AQI).  However, bushfire smoke is smaller and typically PM0.7 to PM1.5 microns. The microscopic size of these particulates allows them to penetrate even deeper into the pulmonary regions of the lungs where air exchange occurs (as shown in the image below). 

This impacts everyone, especially people with impaired respiratory systems, such as asthma, weakened cardiovascular function and immune systems that are not yet fully developed, in particular:

  • Those with heart or lung conditions, particularly asthma
  • Pregnant women – whose immune systems are already working harder
  • Young children – whose immune systems are still developing
  • The elderly – whose immune systems might be compromised


Lung diagram  

Unfortunately, the small size of damaging particles and vapours allows them to easily pass through most air conditioning filters. Whilst indoor air is better, it can still have an impact on health. In addition, bushfire smoke’s mix of potentially carcinogenic and hazardous chemicals can have irritating effects to the eyes and throat, and this can increase the risk for susceptible individuals.

CETEC testing on Premium Grade Buildings during some of the worst bushfire haze found that the informed practices of Facilities Managers alongside superior construction eliminated 90% of outdoor environmental pollutants and thus allowing the people in the building to breathe higher quality air when compared to outside.

Informed air conditioning practices such as properly installed filters make a difference. 

 Particulate matter (PM10) concentrations


 Particulate matter (PM2.5) concentrations The reduction in particulate matter (PM10 and PM2.5 ) from outdoor to indoor levels as measured in Premium Grade Buildings, Sydney in January 2020

Whilst the average office building or home will not perform to these standards, levels of indoor air contaminants are expected to be much higher in poorer performing office buildings and homes.

The following are extra measures that can be taken to improve your air quality:

  • In many cases, it will be safer to stay at work than to return home if the home lacks air conditioning with good quality filter
  • Check your local AQI before opening up windows to naturally ventilate the house. The local AQI rating should be at least average or better
  • At home maximise the quality of your air conditioning filters and use the recirculation mode
  • Check for any leaks in air conditioning ducts
  • Surgical masks are not effective
  • Proper fitting of P2 face masks (otherwise known as respirators) are essential to achieve appropriate protection
  • Continue to heed advice from your health departments and consult your doctor if you are in respiratory distress or need assistance with eye/throat irritation
  • Seek qualified occupational or environmental hygiene advice


To learn more or ask for advice please contact us

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