Controls on Indoor Ammonia in New Canadian Homes during the First Year of Occupancy with Reduced Nitrogen Case...

Ammonia (NH₃) influences indoor air and surface chemistry. Its temporal dynamics and sources during early occupancy of new homes is not well characterized. As part of the New Home Air Quality Study (NHAQS), temporal changes in indoor reduced nitrogen, especially NH₃, from preoccupancy through 12 months was quantified in 48 new homes with nonsmoking residents in the Ottawa-Gatineau area from 2019 to 2024. Passive samplers collected target analytes quantified by ion chromatography and liquid chromatography with mass spectrometry. Indoor NH₃ mixing ratios decreased from pre- to postoccupancy and remained relatively stable over 12 months following, consistent with reduced emissions from new materials and increased partitioning surface area upon occupancy. The NH₃ indoor-to-outdoor ratio indicated indoor sources dominated. Indoor NH₃ levels were higher in warmer months, likely due to temperature-driven repartitioning. A generalized linear mixed model identified glass cleaners and resident presence ≥18 h day^-1 as significant positive predictors of elevated NH₃, while oven cleaner use decreased indoor NH₃ levels. A case study of five homes found reduced nitrogen fate depends on surface chemistry, with potential pathways such as carbonyl condensation, and amide and N-heteroaromatic formation shaping household-specific patterns. This work provides new insights on how homeowners may recognize and reduce NH₃ sources to improve indoor air quality.