Wildfire and bonfire smoke indoors: protecting your air
In one line: during an outdoor smoke event, your best defence is to keep the smoke out (seal up) and clean the air that's already inside (run a high-CADR purifier). Bonfire season and wildfire smoke both spike outdoor PM2.5, and a lot of it gets indoors.
Why it matters
Wood and vegetation smoke is dense with fine PM2.5 — the particle size that reaches deep into the lungs. On a bad wildfire day, or around Bonfire Night, outdoor levels can climb far above normal, and homes are not airtight: that smoke seeps indoors through gaps, vents and every door opening. Indoor levels can stay elevated for hours after the outdoor peak passes.
What to do during a smoke event
- Seal up. Close windows and external doors; if you have trickle vents or extractor fans drawing outdoor air, consider closing/limiting them while smoke is heavy.
- Create a clean room. Pick one room (ideally a bedroom) and run a high-CADR air purifier there continuously so at least one space stays clean.
- Run the purifier hard. This is the time to use a higher speed — clearing the spike matters more than quiet right now.
- Watch the numbers. A cheap PM2.5 monitor shows when indoor levels rise and when the purifier has brought them back down.
- Avoid adding indoor sources — no candles, frying or the wood burner while outdoor smoke is high.
Particles and smell
A HEPA/MERV-13 filter clears the PM2.5 particles; the lingering smoky smell needs activated carbon. For repeated smoke exposure, a unit with both is ideal.
Next step
For smoke-specific picks and deeper guidance see smokeallergy.co.uk, or the evergreen air purifier for smoke guide.
FAQ
Should I open windows to "air out" the smoke? Not while outdoor smoke is heavy — that lets more in. Seal up and filter; ventilate once the outdoor air has cleared.
How big a purifier do I need for a smoke event? Prioritise high CADR for the room so it can clear spikes quickly; size it for at least 5–6 air changes per hour.