A gas flame is a small combustion plant running inside the home. At the high temperatures of a hob burner, nitrogen and oxygen from room air combine to form nitrogen oxides (NOx), mainly nitrogen dioxide (NO2). Incomplete combustion adds carbon monoxide (CO), formaldehyde and ultrafine particles. Condensing boilers are usually room-sealed and flue outside, but hobs and ovens vent directly into the kitchen, and in open-plan layouts the pollution soon reaches the rest of the home.
The health evidence is well established. NO2 inflames the airways and makes them more reactive to allergens. A widely cited meta-analysis linked gas cooking to a 42% higher risk of current asthma in children, and later modelling has attributed roughly one in eight childhood asthma cases in gas-cooking households to stove emissions. Monitoring studies routinely record kitchen NO2 peaks above the UK one-hour outdoor limit of 200 µg/m³, far beyond the WHO guideline of 25 µg/m³ as a 24-hour average. We compare these indoor peaks with city street air in why your gas stove is a greater risk than outdoor smog.
Ventilation is usually offered as the answer, but it does less than people assume. Many UK kitchens have recirculating cooker hoods. Their grease and charcoal filters catch cooking fumes and odours but do little to capture NO2 or CO, so the gases go straight back into the room. Ducted extractors perform better, but only when they are correctly sized, vented outdoors and actually switched on, and field studies consistently find that most households use them rarely, if at all.
The only reliable fix is to remove the source. Induction hobs produce no combustion products at all, and heat pumps take the flame out of the heating system altogether. For property managers and homeowners who want to protect their occupants, electrification is a health intervention as well as a climate measure. Our guide to electrifying the home explains how to plan the switch.