Domestic Liquefied Petroleum Gas and Natural Gas Stoves as an Important Source of Indoor and Outdoor HONO and NO x

Liquefied petroleum gas (LPG) and natural gas (NG) stoves emit nitrous acid (HONO) and nitrogen oxides (NOx), two critical atmospheric pollutants, yet their emission characteristics and impacts are not fully understood. This study characterized HONO and NOx emissions and evaluated the influencing factors for both stove types. LPG combustion consistently demonstrated higher emission factors (EFs) than NG. At a high power, HONO and NOx EFs from LPG reached 110 ± 7 and 1476 ± 39 mg kg–1 of fuel, respectively, compared to 56.0 ± 1.4 and 1032 ± 34 mg kg–1 of fuel for NG. The emissions increased with the power level and duration but decreased in the presence of cookware, indicating previous simulations without cookware likely overestimated EFs. Moreover, NG combustion exhibited higher NO2/NO emission ratios (∼3.3) than LPG (∼0.7) across all power settings, attributable to the lower flame temperature of NG. The environmental impact of residential stoves extends beyond indoor air, contributing significantly to outdoors. For instance, HONO emissions from residential stoves (3.1 ± 0.1 kt year–1) exceed those from gasoline vehicles (0.6 ± 0.2 kt year–1) in China. These findings highlight the significance of domestic gas stoves in atmospheric chemistry and provide key data for refining the HONO emission inventories.