If you cook with gas, the kitchen is not the only room it changes. In six homes, a long bake in a gas or propane oven raised benzene in the bedroom farthest from the kitchen, and in three of them it stayed above a California health benchmark for five hours or more.
The benzene came from the flame, not the food. In the one house where the paper describes a range hood test, kitchen benzene passed the same benchmark within an hour with the hood off or on high.
The study
A Stanford-led team (Yannai Kashtan, with Rob Jackson supervising) published the study in 2023 in Environmental Science & Technology. Between January and December 2022 they measured 87 stoves in 14 counties of California and Colorado, in private homes, apartments and several short-term rentals, using a real-time benzene analyzer. To separate the fuel from the cooking, burners were tested boiling tap water in the same pot, and ovens were tested empty.
What they found
Gas and propane burners and ovens gave off benzene at detectable, repeatable levels. Mean emissions were 2.8 micrograms per minute for a gas burner on high (95% CI 1.7 to 4.6) and 5.8 for a gas oven at 350°F (95% CI 3.3 to 9.7). Propane burners on high and propane ovens averaged 5.5 and 6.5, higher, but not by a statistically clear margin.
10 to 25 times more benzene from gas and propane burners and ovens than from electric coil and radiant alternatives, per the authors. Induction was indistinguishable from zero.
Electric coil and radiant tops on high averaged 0.28 micrograms per minute, about 10% of gas, and electric ovens 0.23, about 4%. The food made no measurable difference: pan-fried fish and bacon, cooked on induction so the stove could not contribute, gave off no detectable benzene.
In 17 kitchens, one gas or propane burner on high or an oven at 350°F for 45 minutes raised benzene above the starting level every time. In 9 of 33 tests (29%) it went past the upper range the authors cite for secondhand tobacco smoke.
The bedrooms
In six houses the team set the oven to 475°F, a bread-baking temperature, for an hour and a half, then turned it off and kept measuring for another six and a half hours. Interior doors were open and no fans ran. They sampled the bedroom farthest from the kitchen, about 8 meters down the hall in five houses and about 4 meters in the sixth.
Bedroom benzene peaked at 5 to 70 times its starting level across the six houses.
In the worst house, bedroom benzene reached 8.9 ppb, stayed above 1 ppb, the California 8-hour benchmark for non-cancer effects, for more than 5 hours, and averaged 2.8 ppb over 8 hours, 23 times its baseline. It also stayed above California’s acute benchmark of 8 ppb for more than 20 minutes. In a second house, benzene peaked at 4.2 ppb and stayed above 1 ppb for the full 8 hours, averaging 2.4 ppb, 26 times its baseline. A third peaked at 2.9 ppb and stayed above 1 ppb for more than 5 hours.
Why it happens
Benzene forms when gas burns in a flame without enough oxygen, the same partial combustion that makes carbon monoxide. The two rose together in this study (r² 0.67). Stove brand and age showed no relationship to emissions. For a typical meal, one burner on high, one on low and the oven at 350°F for about 30 minutes each, the authors estimate roughly 100 micrograms of benzene (95% CI 70 to 190).
The limits, stated plainly
- Six houses is not a survey. The worst one had the highest-emitting oven in the whole study.
- 475°F for 90 minutes is a heavy bake, not a typical weeknight dinner.
- In three of the six houses, bedroom peaks stayed under 1 ppb (0.69, 0.78 and 0.70 ppb).
- Nobody’s actual exposure or health was measured. The authors say further research is needed to assess actual exposures and health effects.
- These were California and Colorado homes, not Portland or Vancouver houses.
- The range hood was tried in two houses, and the paper’s text describes the result for one.
What survives: a gas flame makes benzene, and in some homes it travels to the bedrooms and lingers.
What changes it
Switching fuel. Induction measured no detectable benzene and electric coils about a tenth of gas. Short of that, the authors say concentrations depend on ventilation conditions and home size, which is partly why the same test raised one bedroom far more than another. The ovens themselves also differed: the three lowest bedrooms were in houses whose ovens emitted less.
What gets lost in the gas stove argument
The public argument over gas stoves has centered on nitrogen dioxide and asthma. By the authors’ account, nobody had measured benzene emission rates from home stoves before this study, and the EPA’s emission factor came from utility-scale boilers, not kitchens. The authors estimate about 7,200 kg of benzene a year from US stoves alone, against the EPA inventory’s 4,300 kg for all residential gas appliances combined.
Leaks are not the main story either. Burning gas gave off 70 to 640 times more benzene than a typical leak from a stove that is off.
What the data supports
- Run the hood, vented outside, whenever a burner or the oven is on. The hood alone was not always enough, so add outdoor air too. That second step is general ventilation advice, not something this study tested.
- Do not heat the house with the oven. The authors ran into it in homes and call it not recommended.
- On long, hot bakes, expect the effect to reach past the kitchen.
- If you are replacing a range, induction and electric removed most or all of the benzene.
Bottom line
A gas oven can raise benzene in rooms far from the kitchen for hours. How far and how long depends on your house.
First step: next time the oven is on, turn on the hood and crack a window.
illumenair measures VOCs and carbon monoxide room by room in Portland and Vancouver homes. A total VOC reading is not a benzene test. Call 971-363-5626, email info@illumenair.com or visit www.illumenair.com.
Reference: Kashtan YS, Nicholson M, Finnegan C, Ouyang Z, Lebel ED, Michanowicz DR, Shonkoff SBC, Jackson RB. “Gas and Propane Combustion from Stoves Emits Benzene and Increases Indoor Air Pollution.” Environmental Science & Technology, 2023;57(26):9653. doi:10.1021/acs.est.2c09289.