Wildfire Smoke – Testing HEPA Air Purifiers in Australian Homes

Source: ABC News, August 2, 2025 ABC

Summary

A study in Australia evaluated how effective portable air purifiers with HEPA filters are at removing indoor smoke particles from wood heater emissions (as part of bushfire or controlled burn smoke infiltration). Key findings include:

• HEPA filter units reduced indoor PM2.5 by 30% to 74% during controlled burns (depending on home sealing, purifier capacity, and outdoor conditions). ABC

• Homes that are less airtight (“leaky”) saw more smoke ingress, meaning even strong purifiers struggle if outdoor smoke continually seeps in. Conversely, tighter homes had better results (50% to 77% reduction in US studies under similar conditions) due to less infiltration. ABC

• Variation in performance is large; besides filter quality and purifier CADR, how well the purifier is sized and placed matters a lot. ABC

Understanding and Analysis

This case illustrates practical constraints in real homes versus ideal lab settings. Some key points:

1. Airtightness is crucial: Even the best purifier can't completely control indoor air quality if outdoor smoke continuously enters due to leaks. This underscores the importance of not only filtration but also building envelope improvements (window sealing, door weatherproofing, etc.).

2. Matching CADR and room size/context: A purifier must be appropriate to the space. Undersized units will show significantly worse performance.

3. Realistic expectations: The measured reductions (30-74%) mean that while purifiers help, they do not completely eliminate smoke exposure. They reduce risk, improve comfort, and reduce particulate load—but people sensitive to smoke may still suffer. This is especially relevant for vulnerable groups (children, elderly, those with respiratory issues).

4. Lifestyle and behavior matter: If windows are opened, cooking adds smoke, or the purifier is not running continuously, gains will be less. Proper usage matters (run continuously during smoke events, place purifier centrally or where people spend time).

5. Policy implications: In areas prone to wildfire smoke, building codes might emphasize airtight design, and public health guidance could promote use of air purifiers (and maybe subsidies) for vulnerable populations.

Conclusion

Portable HEPA air purifiers are effective in reducing indoor smoke during wildfire events, but their performance depends heavily on home construction, purifier size, and usage. For stakeholders, including homeowners and policymakers, combining filtration with improved building sealing and proper usage strategies offers best outcomes.