How wildfire smoke infiltrates your home—and how to get rid of it

ByTim Vernimmen

Published October 13, 2023

• 5 min read

Wildfires are becoming increasingly common, lengthy, and intense, due to climate change. In addition to endangering lives, homes, and the environment, the smoke they cause has health risks, including respiratory and heart disease.

Increasingly popular portable air cleaners can remove one component of smoke from the air, the small but solid smoke particles. But a new study in the journal Science Advances reveals they do very little to remove other components of smoke called volatile organic compounds. Some of these are toxic, while many others can cause irritation and breathing difficulties.

(Learn more about how wildfire smoke affects your body.)

Even if you haven’t been personally exposed to wildfire smoke, you’re likely still familiar with these volatiles—they are the odorous and hard-to-remove compounds coating your skin, hair, and clothes after sitting near a campfire or inside a smoky room.

Volatile smoke components are unexpectedly persistent, says atmospheric scientist Jienan Li of Colorado State University. “We’ve found that they penetrate deeply into various surfaces around the house, from where they continue to be emitted for many hours, days, sometimes even weeks.”

Fancy cocktails

Given the rate at which the volatiles continue to be released, the best portable air cleaners tested in the experiment would have needed to clean the air about 20 times faster to keep up, says Li. “Though they work well for particles, I think roughly 4 out of 5 portable air cleaners are nowhere near as effective for volatiles. And as soon as you turn the cleaner off, volatile concentrations go up again.”

Thankfully, says lead researcher Delphine Farmer, also at Colorado State University, there is a straightforward and affordable way to reduce these unexpected emissions from surfaces, which is simply to dust, vacuum, and mop. “This reduces emissions by about 40 percent right away.”

Though wildfires are uncomfortably common in Colorado, Li, Farmer, and colleagues did not wait for natural smoke to drift in to test these cleaning methods. Instead, they created their own in test house used to study energy efficiency. “A student who’d worked as a bar tender introduced us to a device used to make fancy cocktails that heats up pine wood chips to just the right temperature to produce a lot of smoke,” says Farmer.

That may not sound like a very good approximation, but Farmer, who has been involved in earlier studies that involved flying small aircraft into smoke plumes to study their chemical composition, says the smoke produced by the little device was remarkably similar to the real thing.

A good rinse

After two weeks of artificial smoking events, the researchers were surprised to find that even after opening doors and windows for hours, the levels of volatiles in the air would go right back to the same level they started at quickly after the house was closed off again. So, they resorted to surface cleaning.

“We dusted and vacuumed and then mopped—in the order I was taught by my mother—and then used a cleaning solution recommended by the Red Cross,” says Farmer, “consisting of water, trisodium phosphate, and a water-based commercial multipurpose cleaner, which works very well.”

But Farmer, Li, and colleagues only cleaned horizontal surfaces like floors and tabletops, not the walls and ceilings, which may be where the remaining emissions originated. So, if you’re keen to thoroughly rid your house of remaining smoke volatiles, you may see an even bigger benefit from cleaning the surfaces they missed.

(Orange, smokey skies are the future. Here’s how to prepare.)

The researchers warn against using chlorine-based cleaning products or heavily scented ones, however, which will likely release some volatiles of their own and may also interact with the smoke volatiles to create new and equally unwelcome gases. (The same goes for air cleaners that release chemicals.)

Limiting the amount of difficult-to-clean surfaces—think of curtains and carpets, or any other nooks and crannies— in a house regularly exposed to wildfire smoke may also be a good idea, though the researchers stress that they don’t really know yet which surfaces are more likely to absorb volatiles.

Investigating an inferno

Cleaning surfaces to clean the air—it’s counterintuitive, but it turns out to be very effective, even when the wildfire is ongoing, says Li. “Cleaning reduces current emissions from surfaces as well as enhance their ability to take up volatiles that continue to come in, increasing air quality indoors.”

The same principle very likely applies to other pollution sources, such as cigarette smoke, exhaust fumes, or industrial pollution.

“Cleaning surfaces helps,” says Farmer, “and so does opening the windows when the outside air is at its cleanest, as pollutants tend to concentrate inside our homes.”

While these results were found in a controlled setting, scientists who have studied the effects of large wildfires say these cleaning methods are likely still helpful.

“This paper is enormously helpful for the interpretation of our own data obtained in smoke-impacted homes after the [very destructive] Marshall Fire [that raged in Colorado two years ago],” says atmospheric chemist William Dresser of the University of Colorado Boulder, who was not involved in the current study.

“In this study, small amounts of smoke were released indoors under very controlled conditions. In contrast, during the Marshall Fire, huge amounts of smoke were ingested by buildings. And yet we find very similar results for the timeframe of how long different compounds of smoke are retained.”

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