Effect of relative humidity on chemical off-gassing in residences

Relative humidity (RH) is an important parameter associated with occupant comfort in buildings. However, the effects of RH on indoor source off-gassing and interactions between air pollutants and indoor materials are poorly understood. For this study, air samples were collected in residential buildings to characterize “background” concentrations of volatile organic compounds (VOCs) in air. The interior space was then humidified for several hours prior to collection of another air sample to characterize the effects of increased RH on VOC concentrations. Samples were analyzed by GC/FID with abundance “binning” by elution time. Some samples were also analyzed using GC/MS to identify specific VOCs. Results indicate that increasing RH is associated with increases in VOC concentrations in residential indoor air. Many of the chemicals that show enhanced off-gassing are associated with architectural coating, moth repellents, and cleaning agents. The results of this study are novel and may have implications with respect to health effects associated with damp buildings and increased respiratory effects of children during sleep in bedrooms with elevated RH.