How human activities and ventilation systems impact indoor air composition and chemistry in buildings

As people in the U.S. spend 90% of their time indoors, their exposure to indoor air pollutants released during the use of household consumer products cannot be overlooked. Studies have shown that consumer products such as disinfectants, cleaning agents, and personal care products (PCPs) contain complex mixtures of volatile organic compounds (VOCs). Monoterpenes, added as active ingredients in cleaning agents and fragrances, are commonly detected in these products. Monoterpenes can react with ozone (O 3 ) and initiate the formation of secondary organic aerosol (SOA). Siloxanes, another category of compounds commonly found in PCPs, can bioaccumulate and may adversely impact the environment and human health. Most prior studies have evaluated chemical emissions from these products using offline techniques, such as sorbent tube sampling followed by gas chromatography-mass spectrometry (GC-MS). Few studies have been conducted during real-life use of these products in indoor environments. Considering that many indoor activities are often transient, the composition of indoor air can be rapidly altered. Real-time monitoring of indoor VOCs and aerosols is necessary to capture the temporal variations in emissions during indoor activities and to evaluate their impact on indoor air chemistry, human exposure, and outdoor air quality. In addition, O 3 also plays an important role in indoor chemistry. Indoor O 3 concentrations are strongly linked to ventilation system operation and occupancy patterns, as the ventilation from outdoors is the major source of indoor O 3 and occupants are a major sink of indoor O 3 . However, studies on how ventilation modes and occupancy impact spatiotemporal distributions of indoor O 3 are limited. Hazardous chemical incidents can potentially be another unexpected source of indoor pollutants, releasing volatile chemicals which can be transported to indoor environments via building ventilation. Evaluation of air, water, and soil contamination and human exposure risks is critical in the emergency ...