Cleaning floors and surfaces is the most effective way to reduce a major type of air pollution from wildfires that can persist inside buildings.
Smoke from wildfires contains pollutants including particulates, carbon monoxide and chemicals known as volatile organic compounds (VOCs). Many of these VOCs can be dangerous to people’s health. Formic acid, for example, can irritate the eyes and nose, while a compound called furan is a possible carcinogen.
“There’s been an increasing number of wildfire events across the globe,” says Delphine Farmer at Colorado State University. “So we wanted to study the chemistry of wildfire smoke and how it interacts inside buildings.”
To replicate wildfire conditions, Farmer and her colleagues injected smoke from burning pinewood chips into a test house 24 times over the course of two weeks.
They found that the VOCs tended to collect on surfaces in the house, but once the smoke dissipated, they would be released into the air again.
The team also found that some VOCs were buried quite deep into surfaces, which suggests that the compounds could take weeks or months to be re-emitted, says Farmer.
In the second part of their study, the team used a range of ways to clean the house after smoke exposure.
Air-purifying measures, which included opening windows and running air filters, were useful at reducing VOCs quickly. However, after these measures stopped, VOCs rapidly filled the air to earlier concentrations.
Surface-cleaning activities, such as dusting, vacuuming and mopping the floor with a commercial cleaner, were the most effective and long-lasting way to lower VOCs in the air. Concentrations of the most common compounds, including formic acid, formaldehyde and furan, dropped between 19 and 50 per cent after cleaning.
“I was surprised to see just how much better surface cleaning is,” says Farmer. “But it’s because you are addressing the problem at the source.”
The harmful compounds that we see in wildfire smoke are commonly found in outdoor air pollution, she says. “So even for people who don’t live in wildfire zones, the principle of simply cleaning can improve indoor air quality a lot.”