Portable air purifiers with high-efficiency particulate air (HEPA) filters could help millions of Australian families enjoy healthier indoor air during major bushfire events, a new study has found.

As Australia prepares for a difficult bushfire season, a study by the CSIRO has found that HEPA filters which are fitted in portable air cleaners have the potential – when used appropriately – to improve indoor air quality by 30-74 percent during prescribed burns and bushfire events.

Published in Public Health Research & Practice, the study involved researchers monitoring indoor and outdoor concentrations of fine particular matter – otherwise known as PM2.5 – during prescribed burn periods.

They calculated improvements to indoor air quality in nine homes when operating a portable air cleaner which were fitted with HEPA filters during a smoke episode.

The effectiveness of the filters was found to be dependent upon whether the home was compliant with the National Construction Code as homes with greater levels of airtightness are more efficient at preventing the infiltration of outdoor smoke.

The latest research comes as Australia faces the prospect of longer bushfire seasons and more intense bushfire conditions.

A previous CSIRO study showed that extreme fire weather days have increased in Australia by 56 per cent over the last four decades.

Whilst Australia’s air quality is generally good, this can be impacted by extreme events such as bushfires and wood heater emissions.

During the Black Summe Bushfires of 2020, at least 80 percent of Australians were exposed to smoke pollution, which was significantly associated with 417 deaths.

All up, Research from the University of Tasmania has shown around one-third of the Australian population is at elevated risk of developing smoke-associated illnesses during extreme smoke events.

These include 2.7 million Australians who are affected by asthma and around 7 million more who are at elevated risk of developing health problems during extreme smoke events.

In addition to actual bushfires, smoke pollution can be generated during controlled burns which are undertaken to reduce fuel loads and to mitigate risks associated with uncontrolled bushfires.

A range of portable air cleaners are available throughout Australia. However, these need to be fitted with a HEPA filter in order to be effective in trapping harmful smoke and reducing particulate matter indoors.

A HEPA filter refers to a filter that is certified to the HEPA standard as removing almost all particles (dust, smoke, dirt, moisture, bacteria etc.) which are small enough to be inhaled and penetrate deep into the lungs or even into the bloodstream.

Lead author and CSIRO scientist Dr Amanda Wheeler said the results deliver important evidence for agencies when providing advice during extreme weather events.

Whilst agencies have often recommended that vulnerable individuals stay inside and use portable air purifiers with HEPA filters to reduce their exposure to smoke risks, evidence that these in fact reduced exposure or health risks to fine particulate matter has been limited prior to the latest study.

“Staying inside and closing windows and doors during extreme smoke events is important, but ultimately what provides protection against smoke pollution indoors are air purifiers fitted with HEPA filters,” Wheeler said.

“Using more than one, if possible, inside houses is likely to lead to improved health outcomes.

“While the research was focussed on prescribed burns, the findings are relevant for protection during bushfire events more generally.

“They demonstrate that any smoke emissions, including from neighbouring houses’ wood heaters can be managed better.”


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