Keep wildfire smoke out of your home: Expert advice to avoid hazardous conditions

Fueled by high-speed Santa Ana winds, the fast-moving Palisades Fire near Los Angeles is producing dangerous smoke. Below you can see where smoke conditions are most dangerous and visual guide to improving air quality inside your home during a wildfire.

Air quality in Los Angeles area impacted by wildfire smoke

The Palisades Fire, located between the beach towns of Santa Monica and Malibu remained uncontained after burning nearly 3,000 acres as of Wednesday morning.

How to keep wildfire smoke out of your home

Paste BN interviewed two indoor air quality experts in 2023 who offered the following advice on how to keep wildfire smoke out of your home:

"If the air quality outdoors is really bad, stay indoors as much as possible," says William P. Bahnfleth, an engineer and professor of architectural engineering at Penn State University. "If you must go out in the smoke wear an N95 mask outdoors, and avoid heavy exertion."

Because staying indoors is your best protection from toxic smoke, experts recommend giving your house a wildfire checkup.

Professor of Civil and Environmental Engineering at Virginia Tech Linsey Marr says, "The overall goal is to keep the outdoor air outside and to clean the indoor air as much as possible." Marr and Bahnfleth offer these tips:

How to filter out wildfire smoke in your home

◾ Keep your windows closed.

◾  “If your system brings in outdoor air, turn off the outdoor air supply. Outdoor air is often brought in by an energy recovery ventilator that can be switched off independently,” says Bahnfleth.

◾ If you have central HVAC, put in the highest efficiency filters that they can accommodate (MERV 11 or higher desired), and set the fan to run continuously. Residential HVAC systems usually recirculate air and do not bring in outdoor air so by running the fan you are using the system as a whole-house air cleaner.

How to improve the air inside your home during a wildfire

◾ Run bathroom and kitchen exhaust fans only as needed. They end up pulling outdoor air into other parts of the residence.

◾ If you have a portable air filtration unit, like a HEPA air purifier that removes particles from the air, run it on high.

◾ If you have a window-mounted air conditioning unit, check to see that the filter is installed correctly. Run it with the fan on high to circulate air through the filter and remove as many particles as possible. Most units use recirculated air only and do not pull in outdoor air. A small minority have a setting that allows you to control the amount of outdoor air, and you should set these to zero outdoor air.

Build your own wildfire smoke air filter

If you cannot buy commercial portable air filters, you can make do-it-yourself air cleaners. Start with a filter attached to a box fan and consider making a Corsi-Rosenthal box. This kind of makeshift air cleaner was in use for wildfire smoke mitigation before the COVID-19 pandemic.

If the smoke is still bothering you (coughing, tightness or burning in the nose or throat, headache), you may want to wear a high-quality mask.