Keeping wildfire smoke out of the house

Smoke gets into a house through open windows and doors, and through fans and HVAC systems that pull in outside air. It also leaks in through small gaps around closed windows and doors. The biggest health threat in it is fine particles, which can get into the eyes and lungs indoors as well as out. Keeping them down matters most for children, older adults and people with heart or lung disease.

If a fire is very close to the house, it may be best to evacuate, because dense smoke is nearly impossible to keep out. Follow local emergency alerts. These steps are for smoke from a fire that isn't threatening the house.

What you need

• A high-efficiency HVAC filter, such as MERV 13, or the highest rating your system's fan and filter slot can take
• A portable air cleaner sized for the room it will run in, one that doesn't produce ozone
• Spare filters, since heavy smoke means changing them more often
• N95 respirator masks

Steps

1. 1

   Close the windows and doors

   When local officials advise staying indoors, keep the outside air out. Use fans and air conditioning to stay cool, and go somewhere else if you can't stay cool.

   5 min

2. 2

   Set the HVAC system to recirculate

   If the system has a fresh air intake, set it to recirculate or close the outdoor intake damper.

   3 min

3. 3

   Run the HVAC fan

   With a high-efficiency filter in place, set the fan to On instead of Auto, so it filters as much as possible while the air is poor.

   2 min

4. 4

   Close the window unit's damper

   On a window air conditioner, close the outdoor air damper. If it can't be closed, have other cooling ready, such as a fan. Use a single-hose portable air conditioner sparingly, because it can bring more smoke in.

   3 min

5. 5

   Run the air cleaner where people spend the most time

   Run it as often as possible on its highest fan speed.

   2 min

6. 6

   Stop the indoor sources

   Smoking and vaping add particles indoors, and so do gas, propane or wood-burning stoves and furnaces. Aerosol sprays, frying or broiling, candles, incense and vacuuming without a HEPA filter add more.

   5 min

7. 7

   Check the filters

   Look at the air cleaner and HVAC filters often, and change them when they look dirty.

   5 min

When the air improves

Whenever the outdoor air improves, even for a while, air out the house. Open the windows or the HVAC fresh air intake, and run the kitchen and bathroom exhaust fans. Check the outdoor air on AirNow.gov or your state air quality website.

Cleaning up ash afterward

Children, older adults and people with heart or lung disease, such as asthma, shouldn't help with the cleanup. Wear gloves, long sleeves, long pants, shoes and socks, plus an N95 respirator. Don't dry sweep. Mist hard surfaces with water first, then wet mop, and use a HEPA vacuum if you vacuum.

If something goes wrong