How to Improve Home Air Quality: What the Measurements Show

Gas stoves raise indoor NO2 by 4.0 ppbv and it reaches the bedroom. Four home air quality interventions ranked by what randomized trials actually measured.

By Hydra Editorial

Gas and propane stoves raise long-term indoor nitrogen dioxide exposure by 4.0 ppbv on average, according to a 2024 Science Advances study that measured NO2 in more than 100 US homes. The pollution did not stay in the kitchen. It reached bedrooms down the hall and persisted for hours after the burners were off.

Which indoor sources matter most?

Combustion and particulates dominate.

Gas cooking. The Stanford-led Science Advances analysis estimated that gas and propane stoves are responsible for roughly 200,000 current cases of pediatric asthma in the US (95% CI -20,000 to 410,000, a confidence interval worth noticing). A separate 2022 analysis in IJERPH put the population attributable fraction of current childhood asthma from gas stove use at 12.7% (95% CI 6.3% to 19.3%), an estimate that has been contested by other researchers and should be read alongside its wide interval. Exposure was not evenly distributed: households with American Indian and Alaska Native respondents saw the highest stove-attributable NO2 at 6.8 ppbv, roughly 60% above the US average.

Fine particulates. Randomized sham-controlled trials show portable air cleaners reduce indoor PM2.5 by around 56% on average, or about 20.9 µg/m3, with a measurable knock-on effect on systolic blood pressure.

What has actually been measured to work?

Four interventions, in order of evidence strength:

  1. HEPA filtration in the rooms you occupy most. Ten randomized trials, a 55.9% average PM2.5 reduction, and a roughly 4 mmHg systolic blood pressure effect. A 2026 bedroom-focused crossover trial in 33 older adults cut bedroom PM2.5 from 8.3 to 1.3 µg/m3 and 24-hour personal exposure from 12.4 to 5.1 µg/m3.
  2. Range hood vented outdoors, used every time you cook. The Science Advances measurements found NO2 spreads through the home and lingers, which is the argument for capturing it at the source. Researchers note that many range hoods either do not vent outdoors or capture poorly.
  3. Reducing combustion sources. Induction cooking removes the NO2 and benzene emission pathway entirely. The same Stanford group has documented gas stoves as a benzene source.
  4. Ventilation during and after cooking. Simple, unquantified in these particular studies, and the cheapest of the four.

The measurement point is worth making. Indoor air is largely unregulated, invisible, and varies hour to hour with what you are doing. It is one of the few exposures where a cheap sensor changes what you know about your own environment.

The bottom line

  • Gas and propane stoves raise long-term indoor NO2 exposure by 4.0 ppbv on average, and the pollution reaches bedrooms, not just kitchens
  • An estimated 12.7% of current US childhood asthma has been attributed to gas stove use, though the confidence interval is wide (6.3% to 19.3%) and the estimate is contested
  • Portable HEPA cleaners cut indoor PM2.5 by roughly 56% in randomized trials, with a measurable systolic blood pressure effect

Frequently asked questions

Are gas stoves actually bad for indoor air?
Measured NO2 in over 100 US homes showed gas and propane combustion raises long-term exposure by about 4.0 ppbv, with levels persisting for hours after cooking and spreading beyond the kitchen. Estimates of the resulting asthma burden vary between research groups and carry wide confidence intervals, so the exposure finding is more solid than the burden estimate.
Where should you put an air purifier?
The randomized trials with the clearest blood pressure results placed cleaners in bedrooms, where people spend the longest continuous stretch of time. A 2026 crossover trial using a single bedroom unit reduced 24-hour personal PM2.5 exposure from 12.4 to 5.1 µg/m3.

Sources

  1. Kashtan Y et al., 2024. Nitrogen dioxide exposure, health outcomes, and associated demographic disparities due to gas and propane combustion by U.S. stoves. Science Advances 10:18.
  2. Gruenwald T et al., 2022. Population Attributable Fraction of Gas Stoves and Childhood Asthma in the United States. IJERPH 20(1):75.
  3. Walzer D, Gordon T, Thorpe L, et al., 2020. Effects of Home Particulate Air Filtration on Blood Pressure. Hypertension 76(1):44-50.
  4. Zhu Y et al., 2026. Bedroom Air Purification and Home Blood Pressure. Journal of Clinical Hypertension.
Hydra Editorial

Hydra's editorial team. We write from primary research and cite every study we rely on, with its year and journal. We quantify claims wherever the evidence allows and state plainly where it does not: where a finding rests on a small or single trial, we say so in the text rather than in a footnote.