Practical approaches to determine ventilation rate for offices while considering physical and chemical variables for building material emissions

Indoor air pollutants in offices can be attributed to various sources, including building materials, consumer products, and exhalation from occupants. The required ventilation rate for offices can be determined by estimating the majority of emissions originated from building materials, as an additional determinant factor for ventilation rate, with the assumption of constant ventilation with 100% outdoor air, uniform indoor mixing, and no chemical reactions. In this paper, the validity of these assumptions was investigated by incorporating the effects of various physical and chemical factors in determining material emissions and ventilation rates. Three physical factors investigated were recirculation ventilation, intermittent ventilation and pollutant distribution. Simplified methods using correction factors were proposed to revise the ventilation rate and validated by emission modeling and CFD method. In addition, three chemical factors were discussed. First, 28 building materials were selected from the NRC database and each was subject to determining the ventilation rate. As a result, 28 leading pollutants that are likely to determine the ventilation rate were obtained. Because most of the leading pollutants are reactants rather than products of indoor air reactions, it was concluded that the current ventilation rate determining methods should still be applicable. Additionally, a correction method was proposed for a reaction product such as formaldehyde. Second, the methods to revise ventilation rate based on temperature variation and pollutant concentration in outdoor air were proposed. This study showed that ventilation rate for offices could be determined based on building material emissions in more realistic ventilation and environmental conditions.