When bushfire smoke rolls in, the standard advice is to go inside, shut the doors and windows and stay there. But for offices, schools, childcare centres, aged care facilities, retail sites and apartment buildings, “inside” isn’t automatically safe. A building with the wrong air-conditioning settings, leaky seals or busy automatic doors can end up with indoor smoke levels close to what’s outside. A simple bushfire smoke plan, prepared before the season peaks, is what makes the difference.
This guide draws on the US Environmental Protection Agency’s 2025 best practices guide for improving indoor air quality in commercial and public buildings during bushfire smoke events, adapted for Queensland workplaces. With AFAC’s spring bushfire outlook placing south-east Queensland at increased risk this season, now is the time to get it done.
Why smoke matters for your building and the people in it
Bushfire smoke is a mix of fine particles and gases. The biggest health concern is fine particulate matter (PM2.5): particles small enough to travel deep into the lungs and enter the bloodstream. Short-term exposure can cause coughing, breathing difficulty and eye and throat irritation, and it can worsen asthma and heart and lung conditions. Children, older people, pregnant women, outdoor workers and anyone with existing health conditions are most at risk.
You don’t need to be near the fire front to be affected. Smoke can travel hundreds of kilometres, and research cited by the EPA has found that some commercial and school buildings end up with higher indoor particle levels during smoke events than homes do. Under Australian work health and safety laws, employers also have a duty to manage risks to workers’ health, and poor air quality is part of that picture.
What goes into a bushfire smoke plan
A bushfire smoke plan is simply a written list of actions to take before, during and after a smoke event, with clear responsibilities for who does what. It should cover four areas: your air-conditioning system, the building envelope, entrances and extra air cleaning.
1. Get your air-conditioning system smoke-ready
- Service it now. Check that outdoor air dampers open and close properly, filters fit snugly with no gaps around the frame, and sensors are working. A damper stuck open can pull in large amounts of smoky air.
- Upgrade the filters. Standard MERV 8 filters capture very little smoke. MERV 13 or higher filters remove at least half of the smallest smoke particles on each pass. Ask your HVAC technician what your system can handle without straining the fans, and stock spares, because they sell out quickly once smoke arrives.
- Set up a “smoke mode”. Work out, with your HVAC contractor, the minimum outdoor air your building needs, and how to reduce intake to that level during smoke while keeping the building under positive pressure. Economiser and demand-controlled ventilation settings often need adjusting. Closing outdoor air intakes completely is never advised.
- Run the fans longer. Filtration only happens when air is moving. During smoke events, consider running the system continuously (fan only, to save energy) rather than switching off overnight, or at least start it well before staff arrive.
- Practise the switch. Test moving between normal and smoke mode before the season, and document the steps, so anyone on the team can do it when a smoke alert is issued.
A quick way to check building pressure is to hold a strip of tissue paper at the edge of a slightly open external door. If it blows outwards, the building is under positive pressure and pushing air out. If it blows inwards, smoke-laden air is being drawn in. Kitchen, bathroom and laundry exhaust fans are common culprits.
2. Seal the building envelope
Smoke gets in through gaps around windows and doors, vents, skylights, roof access hatches, loading docks and service penetrations for pipes, cabling and security cameras. Walk the building before the season, check weather seals and fix leaks with caulking, weatherstripping or foam. During a smoke event, tape can be used as a temporary seal until permanent repairs are made.
3. Manage entrances and loading docks
- Limit the use of automatic doors, which stay open longer than needed.
- Direct people to entrances with vestibules, air curtains or revolving doors, ideally on the side away from the prevailing wind.
- Keep both sets of vestibule doors closed, and schedule deliveries or loading dock use for short windows or after hours.
- Never lock exits to keep smoke out. Use signage such as “Please use other door” instead, so emergency egress and accessibility are maintained.
4. Add portable air cleaners and a cleaner air room
Portable air cleaners with HEPA filters are especially useful in buildings with split systems or no central air-conditioning, and near doors that must stay in use. For childcare centres, aged care and health settings, consider setting up a “cleaner air room”: a closed room with enough air cleaning capacity for its size, where the most vulnerable people can spend the worst hours of a smoke event. Size units by their clean air delivery rate (CADR) against the room volume, and plan where they’ll go before you need them.
In one EPA-supported study during an extreme smoke event, indoor fine particle levels in a childcare centre dropped close to zero once HEPA air cleaners were installed, while outdoor levels stayed extremely high. In a nearby school classroom with no extra filtration, indoor levels tracked the outdoor smoke almost exactly.
5. Monitor indoor air
Low-cost indoor PM2.5 sensors let you compare indoor and outdoor air, confirm your plan is working, and spot when filters are loaded and need changing. Place them away from kitchens, printers and exhausts so they reflect what people are actually breathing. While ventilation is reduced, also pause activities that add indoor pollution, such as cooking, aerosol sprays and vacuuming.
After the smoke clears
- Return the HVAC system to normal settings and flush the building with fresh outdoor air once air quality has improved.
- Replace filters that are dark or smell of smoke, remove any temporary intake filters, and restock for the next event.
- Repair any leaks you found and review what worked in your plan.
- If residue, soot or lingering odour remains inside, get a professional assessment before staff and clients return to affected areas. Most smoke impact is a surface problem that can be cleaned. Our guide to bushfire smoke damage restoration explains what’s involved.
Bushfire smoke plan checklist
Before the season: service the HVAC system, confirm the highest filter rating it can take, stock MERV 13 filters, define and test smoke mode, seal leaks, plan entrance changes and cleaner air rooms, and assign responsibilities.
When smoke is forecast: install upgraded filters, switch to smoke mode, run fans continuously, restrict entrances and loading docks, switch on portable air cleaners and check building pressure regularly.
After the event: return to normal operation, flush the building, replace and restock filters, repair leaks, arrange cleaning where residue remains, and update the plan.
Common questions
Should we shut off outside air completely during smoke?
No. Reduce outdoor air to the minimum your building needs, but don’t close intakes entirely. Too little ventilation lets carbon dioxide and indoor pollutants build up and can leave the building under negative pressure, which draws more smoke in through gaps.
Can any system take a MERV 13 filter?
Not always. Higher-rated filters can add resistance to airflow. Check the filter’s pressure drop against your system’s capacity with your HVAC contractor. If MERV 13 isn’t suitable, use the highest-rated filter the system can handle and add portable air cleaners.
Who should prepare our bushfire smoke plan?
Building owners, facility managers and strata committees usually lead it, with an HVAC professional setting and testing the system changes. For larger or more complex systems, ASHRAE Guideline 44-2024 on protecting building occupants from smoke is the technical reference HVAC engineers use.
Talk to Pircsa
Pircsa works with building owners, facility managers, strata committees and insurers across South East Queensland on fire and smoke damage. If smoke has already affected your building, our assessments are led by Steve Cranston, an ACAC Council-certified Fire and Smoke Damage Consultant (CFSC), who can tell you what needs cleaning, what needs replacing and when independent testing is warranted.
Call 07 3267 7068, email office@pircsa.com.au or contact us online.
Sources
- US EPA, Best Practices Guide for Improving Indoor Air Quality in Commercial/Public Buildings During Wildland Fire Smoke Events, May 2025 (EPA: Wildfires and Indoor Air Quality)
- US EPA Office of Research and Development, Emerging Approaches to Cleaner Indoor Air During Wildfires (Hoopa Valley and Missoula field studies)
- ASHRAE, Guideline 44-2024: Protecting Building Occupants from Smoke During Wildfire and Prescribed Burn Events (ashrae.org)
- IICRC, RIA and CIRI, Technical Guide for Wildfire Restoration, December 2025 (iicrc.org)
