Comparison of predicted and derived measures of volatile organic compounds inside four new relocatable classrooms

Abstract

Our objective was to develop a process for selecting interior finish materials having low impacts with respect to emissions of toxic and odorous volatile organic compounds (VOCs) for school relocatable classrooms (RCs). A laboratory study identified alternate materials with low VOC emissions. Two pairs of RCs then were constructed. One RC per pair contained standard interior materials; the other incorporated alternate materials. The pairs were sited side-by-side at two California elementary schools in fall 2001. Fifteen target VOCs, including the toxicants formaldehyde, acetaldehyde, vinyl acetate, phenol, toluene, and naphthalene, were measured during school hours over 8 weeks in the succeeding fall cooling season. Indoor minus outdoor VOC concentrations with an advanced HVAC operated were low; only formaldehyde concentrations exceeded 5 p.p.b. Classroom VOC concentrations were predicted based on emission factors (microg/m(2)/h), material quantities and design ventilation rates. These were compared to average adjusted concentrations measured when the occupied classrooms were operating at near the code-minimum ventilation rate. For 16 of the possible 42 comparisons, measured concentrations agreed within a factor of two of predicted the predicted values. Concentrations of six of 10 VOCs were significantly lower in modified RCs though average differences were mostly less than 1 p.p.b. Laboratory-based material testing combined with modeling and field validation to select low VOC-impact interior finish materials helped achieve the aim of providing generally acceptable air quality in new school relocatable classrooms (RCs). The accuracy of the combined process was evidenced by the correct prediction of air quality impacts, though small, due to material VOC emissions when the study RCs were ventilated at code-minimum requirements. The process could be generalized to other manufacturers and classroom types. Material selection also is important to accommodate reduced ventilation rate conditions, which likely occur in many classrooms.