Chemical fingerprints of cooking emissions and their impact on indoor air quality.

Indoor environments host multiple sources of volatile organic compounds (VOCs) that influence the air quality, with cooking being one such significant and complex emission source. VOC emissions from cooking vary with the type of food cooked, ingredients used, cooking methodology, and ventilation, yet their speciation and impact on indoor air remain poorly understood. This study quantifies real-time emission rates of 39 VOCs from three frequently prepared UK meals: stir-fry, curry, and chilli, using a high-sensitivity selected ion flow tube mass spectrometer (SIFT-MS) in a room-scale, semi-realistic kitchen. Across 39 cooking experiments a distinct VOC emission profile for each meal was measured. The emissions were dominated by alcohols (methanol and ethanol, >50% of total emissions), harmful aldehydes (acetaldehyde, 7-23%), and highly reactive monoterpenes (up to 4%). The emissions were found to be influenced strongly by the use of different variants of the same ingredient (freshly chopped and packaged diced onions), spices and cooking behaviours. The secondary chemistry of the resultant VOC emissions was further investigated by simulating the hydroxyl (OH) reactivity and secondary product formation using INCHEM-Py. The model results show that the cooking plumes significantly perturbed the indoor chemistry, with OH reactivity ranging from 50-200 s-1 depending on VOC composition. Further simulations of a typical urban London kitchen revealed recipe-dependent impacts on radical (HO2, RO2) and secondary pollutant (O3, PAN, organic nitrates, formaldehyde) formation. Among the meals tested, chillies exhibited the highest potential for secondary pollutant production, followed by curries. These findings highlight the influence of cooking emissions on indoor air quality and secondary chemistry.