Researchers monitored 27 commercial gas kitchens in California, Pennsylvania and New York. The three all-electric kitchens stayed inside every limit. Gas pilot lights left burning overnight pushed some readings above what the same kitchens recorded during service.
Researchers attached a temperature monitor to a chef’s shoulder during a cooking session of roughly five hours. The average reading was 92°F (33°C). At its peak it touched 106°F (41°C).
One chef on one shift is a small sample, and the scientists treated it that way. But it sits inside a larger study, published on 6 October, that comes to an uncomfortable conclusion for the restaurant trade. In about seven out of ten commercial kitchens that cook with gas or propane, workers were exposed to air pollution, heat, or both at levels above health-based guidelines. The kitchens that cooked only with electricity did not cross a single line.
Gas Kitchens Can Reach Extreme Heat During Service
The paper, “Combustion-Derived Air Pollution and Heat from Gas-fired Appliances in Commercial Kitchens Can Exceed Health-Based Guidelines”, comes from researchers at PSE Healthy Energy, the Stanford Doerr School of Sustainability and New York University’s Grossman School of Medicine, working with chef Christopher Galarza. It was published in Environmental Research Letters. The team says it is the first US study to compare gas, propane and all-electric commercial kitchens under real working conditions.
What was measured
The team monitored 27 kitchens in California, Pennsylvania and New York. Twenty-one cooked with natural gas, three with propane and three were all-electric. Instruments recorded nitrogen dioxide, benzene, carbon monoxide, carbon dioxide, methane and air temperature at locations where staff actually work. Readings were taken during service and again overnight, when the kitchens were closed.
The kitchens volunteered. PSE recruited restaurants, cafés, hotels and similar sites through a public sign-up, with a preference for full-service kitchens that had commercial ventilation hoods. Galarza recruited most of the participating kitchens himself.
The air
Nitrogen dioxide is a by-product of burning fuel. It inflames the airways and raises the risk of asthma. During cooking hours, the hourly average measured outside the hood systems was above the US Environmental Protection Agency’s one-hour standard of 100 parts per billion in 17 of the 24 gas and propane kitchens.
That benchmark was written for outdoor air, not for workplaces, and the researchers use it as a health-based yardstick. The occupational comparison is starker. In one kitchen, a 15-minute average went above 1,000 parts per billion, the short-term workplace limit recommended by the National Institute for Occupational Safety and Health.
Other pollutants also crossed lines. Carbon monoxide went over California’s one-hour guideline of 20 parts per million in three gas kitchens. Benzene, a known human carcinogen, went over California’s one-hour guideline of 8.4 parts per billion in five.
The findings bear on a common assumption, that a good hood solves the problem. The hoods helped, according to the study, which says they reduced pollutant exposure but did not remove it. At worker-relevant locations in roughly two-thirds to seven-tenths of the gas-fired kitchens, concentrations still went over health benchmarks.
The heat
Temperature was recorded in 19 of the gas kitchens. In 13 of them, or about 68 per cent, readings went above 90°F (32°C). That is the high-heat trigger in the heat rule OSHA, the US workplace safety regulator, proposed in 2024, and the level at which California’s indoor heat illness regulations apply. Ten kitchens recorded a maximum above 100°F (37°C), and four went past 122°F (50°C).
Weather was not the explanation. On days when the outdoor temperature stayed under 75°F (23°C), 10 of 13 gas kitchens still went over 90°F indoors. The researchers conclude that the heat comes mainly from the cooking equipment.
Yannai Kashtan, the lead author and an air quality scientist at PSE, told Stateline that nothing here will surprise anyone who has worked a line, since cooks already know these are “intense environments full of heat and pollution.” What the study adds is measurement. He pointed to the physics: a gas flame transfers only part of its heat to the pan, and the rest goes into the room.
Only two all-electric kitchens had temperature data. Both recorded some of the lowest in-service temperatures in the whole study, two of the three lowest. Two is too few to build an estimate on, and the authors do not claim otherwise.
Pilot lights overnight
The overnight finding may be the most unexpected. In about seven in ten of the gas kitchens monitored after closing, levels of nitrogen dioxide, carbon monoxide, carbon dioxide, methane and benzene were higher overnight than during service. Ventilation was switched off, and the pilot lights stayed lit. Seven kitchens went above the 100 parts per billion nitrogen dioxide mark during off-work hours.
Drew Michanowicz, a principal scientist at PSE and a co-author, said some of the highest indoor levels the team recorded came “when no one was cooking at all.” That matters for cleaning crews and for staff who arrive early to open up. He added that the same kind of commercial appliances are used in schools, hospitals and mixed-use buildings, so the exposure probably extends well beyond restaurants. The study did not measure those buildings.
None of the all-electric kitchens exceeded a pollutant threshold at any hour, day or night.
Who is affected
The US restaurant and food service industry employs an estimated 15.7 million people. About five million of them spend all of their working hours in the kitchen.
Galarza, who is a co-author as well as the person who found most of the kitchens, told Canary Media the results show “what it is we’re exposing ourselves to.” In the release, he said that kitchen staff should not have to accept excessive heat or polluted air as part of the job, and that the study gives owners and chefs better information on what equipment choices mean for the workplace.
Rob Jackson, a Stanford professor of Earth system science and a co-author, said burning gas in a restaurant kitchen is as suspect as burning it at home, and that the all-electric kitchens emitted none of the pollution seen in the gas ones. Jackson directs a Stanford programme called Electrification for Health. PSE ran the work under its Methane + Health Initiative. Readers should know that the authors have a long record of research on the health costs of burning gas indoors. Panama Bartholomy, executive director of the Building Decarbonization Coalition, which promotes electrification, welcomed the results in a statement quoted by Canary Media.
What the study cannot say
The sample is small. Twenty-seven kitchens spread across California, Pennsylvania and New York is a modest number, and only three of them were all-electric. Kitchens that agreed to be monitored may not look like the average restaurant, and the researchers did not select them at random. The study measured air and temperature, not the health of the people working in the kitchens. Whether any of these readings has made someone sick is a separate question that this work does not try to answer.
The yardsticks also come from different places. Some were written for outdoor air, some for one-hour exposures, and one is a recommended workplace limit. They are accepted ways of judging whether air is harmful, but they are not all legal limits that a kitchen would be cited for breaking.
What happens next
OSHA’s proposed heat rule has not been finalised. Legal analysts tracking the rulemaking say it has stalled, and that the Labor Department’s regulatory agenda points to a supplemental proposal in December 2026. Until a federal standard exists, OSHA relies on its general duty clause to cite employers for heat hazards, and a number of states, California among them, enforce their own rules.
For owners, the study points to two things that can be changed: how well the kitchen is ventilated and which fuel the appliances burn. Its authors describe both as the main controllable factors behind the air and heat that workers face.