Here’s how smoke chemicals linger in homes after a wildfire

As the planet endures its highest temperatures since the beginning of the industrial era, the resultant fires are leaving problems behind even after the flames are doused.

US researchers say chemicals from the smoke lingers in homes long after the fires have passed.

“This research shows that events like the Marshall Fire in Colorado, the wildfires in Canada and the recent fires in Hawaii present serious exposure potential,” says chemist Professor Delphine Farmer, at Colorado State University, adding “not just when they occur but well after.”

“This paper is a key initial step towards providing actionable and practical information on how to protect yourself and clean your home.”

The research has been published in Science Advances.

When smoke from fires, cigarettes or even a burnt lunch comes through a home, volatile organic compounds (VOCs) are released into the environment. They settle on all surfaces but can stick to soft furnishings like carpets or couches.

“Nicotine reacts on surfaces to create a particularly nasty set of compounds called nitrosamines, which is where the real concern from third-hand smoke that is left behind comes from,” she says.

“Whereas with wildfire smoke, we found there was a huge diversity of organic compounds that stick to surfaces, which then slowly bleed off.”

A women in a mask injects smoke into a see through box
Kathryn Mayer introducing wildfire smoke into the test area. Credit: John Eisele/Colorado State University Photography

The team worked inside a residential testing facility operated by the National Institute of Standards and Technology (NIST). By burning pine wood chips, and injecting smoke into the ‘house’ over several days they were able to create similar particulate levels to the Canadian wildfires earlier this year.

 Then, the researchers opened windows and doors, cleaned, and used an air cleaning system to see what removed the most compounds.

“Surface cleaning activities (vacuuming, mopping, and dusting) physically removed surface reservoirs and thus reduced indoor smoke VOC concentrations more effectively than portable air cleaners, and more persistently than window opening,” the researchers wrote in their new paper.

For the moment, the researchers suggest simple cleaning of surfaces and vacuuming is the way to go, but also clean unused spaces like cabinets and air conditioning systems which could trap harmful compounds.  

“Although this paper focuses on wildfire smoke, our results may apply to other air pollution scenarios, including intensive cooking, infiltration of heavy urban smog, cigarette smoking, or other indoor emission activities,” the researchers add in the paper.

But this isn’t the end of the research. Amounts and types of compounds and their persistence in the environment could change how researchers recommended to clean houses after wildfires. The team is now looking into this. 

“As we continue this research, we would like to know just how effective different cleaning approaches are and when residents should move from relatively simple steps like using commercial cleaning supplies for mopping to more drastic steps like replacing the drywall altogether,” Farmer concluded.

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