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Which? study reveals gas hobs are polluting indoor air
Research shows cooking on domestic gas hobs can cause two of the most harmful air pollutants, NO2 and PM2.5, to exceed WHO guidelines, risking human health
Findings from Birmingham City University underline importance of extractor hoods and open windows while cooking, helping to minimise pollution and mould growth
Cooking on a gas hob can generate more air pollution indoors than levels seen on one of the UK’s busiest roads, according to a snapshot investigation from consumer organisation Which?
The study compared the levels of nitrogen dioxide (NO2) and fine particulate matter (PM2.5) — two of the most damaging outdoor and indoor air pollutants — generated by cooking on gas hobs, an induction hob and London’s Marylebone Road.
The study, conducted in November 2024, asked five volunteers to carry out several cooking scenarios in addition to their normal usage; all windows and doors were kept shut apart from a test scenario where the kitchen was fully ventilated.
Air quality monitors showed NO2 levels rose when gas hobs were used and increased in line with the amount of cooking time and the number of gas rings used. Even in a slow cooking, one ring scenario, NO2 levels more than doubled.
Furthermore, NO2 levels remained elevated for several hours after cooking, suggesting those with open plan homes could be exposed to sustained elevated levels exceeding WHO guidelines. The volunteer using the induction hob experienced only background levels of NO2, mainly from outdoor pollution.
Three volunteers saw PM2.5 levels peak at over 100µg/m³ on several occasions, with one experiencing a peak of nearly 650µg/m³ when frying Padron peppers; two others experienced peaks of over 500µg/m³ when cooking a fry up. The WHO 24-hour mean guidance limit is 15µg/m³.
During the study, NO2 pollution levels near the Which? office on Marylebone Road were recorded at an hourly mean of 33µg/ m³, while PM2.5 averaged 14µg/ m³ over a 24-hour period.
“…our snapshot research shows that once it spikes, air pollution can spread rapidly through the house and linger for long periods of time.”
Emily Seymour, Which? Energy and Sustainability Editor, said: “It’s shocking to think that something as routine as cooking dinner could be releasing harmful pollutants into our own homes, but our snapshot research shows that once it spikes, air pollution can spread rapidly through the house and linger for long periods of time.”
Dr Monica Mateo-Garcia, Senior Lecturer in Sustainable Built Environment at Birmingham City University said: “Cooking with gas hobs can produce high levels of CO2 as well as high peak concentrations of other air pollutants such as particulate matter (PM2.5) and Volatile Organic Compounds (TVOC) from cooking.
“Research conducted by the Centre for Future Homes at Birmingham City University shows that using extractor hoods that vent outside and opening windows and doors while cooking contribute to a quick decay of the indoor pollutants.
“Inadequate ventilation can cause negative impacts on occupant health as well as condensation and mould growth.”
The findings reinforce those from other scientific studies, but significant knowledge gaps remain around the impact of air pollution on the human body. NO2 can exacerbate respiratory conditions in adults and children and is a significant contributor to children developing asthma.
Particulate matter is toxic, with PM2.5 particularly damaging. Particles can travel deep into lungs and enter the bloodstream, reaching every organ of the body and causing changes that promote diseases like Parkinson’s, diabetes, lung cancer, COPD and heart disease, as well as impacting reproductive and foetal health.
