Smoke outside. Build one clean room.
You don't need to seal the house — you need one room where the air is on your side.
Do this now
- Pick one room, close its windows and doors, and run air conditioning on recirculate — never fresh-air intake.
- Make a clean-air machine: a HEPA purifier if you have one; a box fan with a furnace filter strapped to it if you don't.
- Going outside: N95 or KN95, fitted over nose and chin. Cloth masks and bandanas do nothing against smoke.
- Don't add smoke indoors — no candles, frying, fireplace, or vacuuming (it stirs fine particles back up).
- Watch the vulnerable: kids, pregnant people, elders, and anyone with asthma or heart disease feel it first.
Read the number, not the haze
Smoke's fine particles (PM2.5) hurt long before the sky looks apocalyptic. Check the AQI for your address on AirNow: over 100, sensitive groups stay in; over 150, everyone limits time outside; over 200, the clean room is where you live. The nose is a bad meter — you stop smelling smoke you're still breathing.
The box-fan filter
A 20-inch box fan with a 20×20 furnace filter (MERV 13 if possible) taped or bungeed to the intake side scrubs a small room surprisingly well. Point it into the room, run it steadily, and swap the filter when it grays. It's the $40 version of a purifier, endorsed by air agencies for exactly this.
When symptoms speak
Scratchy throat and stinging eyes are expected; wheezing, chest tightness, or asthma that isn't answering its inhaler are not — that's medical care, not toughing it out. Smoke days are also not workout days, indoors or out: deep breathing multiplies the dose.
Do not
- Don't rely on cloth masks or bandanas against smoke.
- Don't run the AC on fresh-air intake or a swamp cooler pulling outside air.
- Don't burn candles, fry food, or vacuum in the clean room.
- Don't exercise hard on heavy-smoke days.
Common questions
What AQI is unsafe from wildfire smoke?
Above 100 is unhealthy for sensitive groups; above 150 everyone should cut outdoor time; above 200, stay in the clean room. Check your address on AirNow.gov.
Do N95 masks work against wildfire smoke?
Yes — a fitted N95 or KN95 filters the PM2.5 particles that do the harm. Cloth masks and bandanas don't.
How do I make a DIY air filter for smoke?
Strap a 20×20 furnace filter (MERV 13 if you can get it) to the intake side of a 20-inch box fan and run it in a closed room. Replace the filter when it turns gray.
Sources — official guidance
Before you lose signal
Save the whole kit to your phone.
This page needs the internet. The NothingLoads app doesn't — all 28 guides, offline search, and your family's own emergency plan live on the phone itself and work in Airplane Mode. Life-safety guides are free for everyone, forever.
Free · about 1 MB · iPhone & iPad · no account · no tracking