Fate and Transport of Pollutants in the Built Environment: Atmospheric Chemistry Moves Indoors

Indoor air quality is a function of dynamic processes in which chemical reactions play a key role by consuming primary emissions and generating secondary contaminants, including secondary organic aerosols (SOA). While outdoor pollution contributes background levels, the composition of indoor air is strongly determined by indoor sources, including occupant activities such as cooking, smoking or cleaning. In indoor environments, low molecular weight organic compounds and reactive species are found principally in the gas phase, while persistent semivolatile compounds tend to accumulate both in the gas phase and on exposed surfaces, including those of airborne particles and settled dust. To meaningfully alter the composition of indoor air, gas phase reactions must occur at rates that are competitive with air exchange rates. Such constraints do not apply to surface reactions, which are favored by the large surface-to-volume ratios found indoors. Indeed, indoor surfaces may present substrates that favor certain chemical reactions such as base catalyzed hydrolysis. As practices consistent with environmental sustainability and zero-energy buildings are incorporated into building construction and operation, new materials with novel emissions and surfaces will be introduced. Characterizing indoor chemistry, with an eye towards mitigation strategies, becomes even more important in such a setting, since its impact on human exposures will be amplified as a consequence of tighter building envelopes and reduced air exchange rates