The highest emitters were cooktops that ignited using a pilot light instead of a built-in electronic sparker. Methane emissions from the puffs of gas emitted while igniting and extinguishing a burner were on average equivalent to the amount of unburned methane emitted during about 10 minutes of cooking with the burner. Interestingly, the researchers found no evidence of a relationship between the age or cost of a stove and its emissions. Most surprising of all, more than three-quarters of methane emissions occurred while stoves were off, suggesting that gas fittings and connections to the stove and in-home gas lines are responsible for most emissions, regardless of how much the stove is used.
Overall, the researchers estimated that natural gas stoves emit up to 1.3 percent of the gas they use as unburned methane. While the U.S. Environmental Protection Agency (EPA) does not report emissions from specific residential natural gas appliances, it does report methane emissions for residential appliances collectively. From stoves alone, the researchers estimated total methane emissions to be substantially more than the emissions currently reported by the EPA for all residential sources.
Larger stoves tended to emit higher rates of nitric oxides, for example. Using their estimate of emissions of nitrogen oxides, the researchers found that people who don’t use their range hoods or who have poor ventilation can surpass the EPA’s guidelines for 1-hour exposure to nitrogen dioxide outdoors (there are no indoor standards) within a few minutes of stove usage, particularly in smaller kitchens.
“I don’t want to breathe any extra nitrogen oxides, carbon monoxide or formaldehyde,” said study senior author Rob Jackson, the Michelle and Kevin Douglas Provostial Professor and professor of Earth system science. “Why not reduce the risk entirely? Switching to electric stoves will cut greenhouse gas emissions and indoor air pollution.”