Wildfire & environment
When Is It Reasonable to Reopen Windows After Wildfire Smoke?
Try brief ventilation when official local air quality has clearly improved, smoke is not visible or noticeable, heat can be managed, and no local instruction says to stay sealed. Do not use a fixed number of hours.
SharedMorrow Editorial · Last reviewed 2026-10-05
Direct answer
Try brief ventilation when official local air quality has clearly improved, smoke is not visible or noticeable, heat can be managed, and no local instruction says to stay sealed. Do not use a fixed number of hours.
Start here
Check local air-quality agencies or an official service such as AirNow and follow the trend, not one reading. Compare indoor and outdoor conditions; if outdoors is cleaner, open a limited set of windows briefly during a cleaner period and watch symptoms or an indoor sensor.
Work through the decision
Keep smoke-prone fresh-air intakes closed until improvement is sustained, then restore ventilation and inspect or replace dirty filters.
Common mistake
Use a more conservative plan for children, pregnancy, older adults, or heart and lung disease, with a cleaner-air room ready. No smoke smell and a cooler evening do not prove fine-particle levels are low enough for prolonged open windows.
When to stop and get help
Stop and move to a cleaner, cooler place or seek medical help for persistent poor air, unsafe heat, breathing difficulty, or chest pain.
Next step
Avoid smoking, candles, frying, and non-HEPA vacuuming while airing out; close again if the condition worsens.