Modeling Secondary Emissions from Indoor Chemical Reactions Initiated by Ozone and Hydroxyl Radicals

Volatile organic compounds (VOCs) can be oxidized by ozone (O3) and hydroxyl radicals (OH•) under a series of reactions to produce secondary emissions indoors in addition to primary emissions. A mathematical model that accounts for ventilation, surface adsorption, oxidant generation, ozone and hydroxyl radicals-initiated chemical reactions was developed for evaluating the pollution loads and concentrations in a ventilated space. The model focused on major chemical reactions that were responsible for stable products from secondary emissions as detected in full-scale chamber experiments. The experiments were simulating a realistic ventilated room and how a source of O3 and OH• would affect the concentrations of VOCs. The modeled results were in line with the experimental results. Alpha-pinene and heptanal were selected to illustrate the model prediction results as an example given their relatively high reaction rates with O3 and OH•. Limitations of the model and the needs for further development were also identified.