The humble gas stove has claimed a place in America’s national psyche in the past month, after studies showed that burning fossil fuels at home can cause asthma and other ailments, on top of releasing emissions that warm the planet. Are there any quick fixes?
The Guardian spoke with air quality experts to find out if air purifiers help reduce pollution from gas stoves and other forms of indoor contaminants. We also asked them to set the record straight on the air-purifying qualities, or lack thereof, of houseplants.
Can air purifiers remove pollutants emitted from gas stoves?
Darby Jack, associate professor of environmental health at Columbia University: Since the main pollutant of concern from stoves is nitrogen dioxide – a gas and not a particle – air purifiers that just have a Hepa [high efficiency particulate absorbing] filter won’t be effective.
Some purifiers contain activated charcoal, which in theory can help with NO2. But I would not be inclined to trust manufacturer claims, and they don’t seem to have been tested rigorously in settings that would be relevant for home kitchens with gas stoves.
Michael Johnson, senior scientist at Berkeley Air Monitoring Group: While Hepa filters are really good at getting rid of particulate matter, that’s about all they will do. It might increase your ventilation a little just because it’s circulating the air a bit, but they aren’t designed to remove nitrogen dioxide or other gas pollutants.
Elliott Gall, associate professor at Portland State University researching physics and chemistry of indoor air quality: Air cleaners typically move air across mechanical filters that are designed, and usually tested, to remove particles. Particles are solids or liquids suspended in air. Gas stove combustion does generate particles, which an air cleaner with mechanical filters can remove. But stoves also emit other classes of pollutants which we are concerned about, including volatile organic compounds and oxides of nitrogen. These are not removed by mechanical filters. Air cleaners with chemical sorbents, like activated carbon, are more likely to be able to remove these compounds from indoor air.
Will air purifiers at least help reduce other forms of indoor air pollution?
Michael Johnson: There are lots of sources of indoor air pollution in addition to gas stoves. Wildfires can cause outdoor and indoor air quality challenges; smoking is certainly a big one. Other things that can cause indoor pollution include printers and pets, vacuuming and dusting, candles, use of aerosols and incense. Sometimes when you get new furniture or shower curtains they can off-gas and release formaldehyde and other VOCs [volatile organic compounds, which are chemicals released from manufactured products]. Hepa filters will help with any type of dust or particulate matter, but not gases like VOCs or carbon monoxide.
During wildfires, which cause outdoor and corresponding indoor air quality challenges, [an air purifier] is a great tool to reduce particulate matter. And it can also help mitigate exposure to the Covid virus.
Misbath Daouda, PhD Candidate in climate and health at Columbia University: Outdoor air pollution can be a potential contributor to indoor air pollution. In the United States, outdoor air pollution is regulated and we’ve been able to decrease ambient levels of all sorts of pollutants. But because indoor air pollution is not regulated, these levels tend to be a lot higher, especially when things like gas stoves or other sources of pollutants are on.
Molly Kile, professor of environmental and occupational health at Oregon State University: An air purifier would improve the indoor air quality by removing pollutants. This would include outdoor air pollution that makes its way indoors. If you live in an area with bad air quality or want to use an air purifier, you need to pick the right one that is sized appropriately for the room it will be used in. And do not use one that creates ozone or says it uses ozone to purify the air. There are a lot of these on the market that are being sold because [they say] ozone will kill bacteria and viruses. Ozone is an air pollutant and you do not want to be adding that to your indoor air! It defeats the purpose of the air purifier.
Back to gas stoves. If air purifiers don’t work, what’s the best way to reduce exposure to emissions?
Molly Kile: Using a ventilation hood that exhausts to the outside of the home. So I would recommend that people use it whenever they turn on their gas stove. If they do not have the ability to have an externally exhausted ventilation hood, then they should open a window or door to get natural ventilation.
Misbath Daouda: Replacing the gas stove is the best way to reduce NO2 in the home and create a healthier environment. But a lot of renters do not have a say on what appliances are in their homes. So for this to be equitable, the onus of replacing the gas should not just be placed on the person who is renting. Really we should be thinking about what regulations could be put in place so that building owners actually have an incentive to upgrade appliances.
Are plants effective purifiers? A famous 1989 Nasa study measured plants’ abilities to purify air. Among the plants tested were ficus, English ivy, mother-in-law’s tongue, deeming them “a promising, economical solution to indoor air pollution”.
Molly Kile: Alas, plants are good for many things but do not purify the air. That’s a myth.
Elliott Gall: Don’t rely on plants to clean indoor air. Think about the amount of plants that you might have inside a building, relative to the volume of the building, and all the other things that are happening in the building, like ventilation. Essentially what’s going on with that plant, in terms of removal of air pollution, is negligible compared to all these other things that are happening.
The Nasa study was set up in a scientifically sound way, and they gave all the relevant information to evaluate the study. A key aspect of this study is that they put plants in sealed chambers, injected pollutants, waited some amount of time and asked: “How much pollutant is left?”
The issue is, how do you take the information that came from that study in sealed chambers and apply it to a very different scenario – a real home? Imagine the result if the sealed chamber test was 90% removal of a pollutant in an hour. It sounds promising, but if you put that plant into a real indoor environment, like a 2,000 sq ft home, you would never realize a 90% reduction of pollutants. But a simple one-to-one translation of sealed chamber test results to real buildings make compelling headlines and marketing language,
So the misrepresentation persists. But the upside to this is that, if you like plants in your living space, they also aren’t degrading your indoor air quality.
Interviews have been edited and condensed for clarity