Lawrence Berkeley National Laboratory

The effect of temperature and humidity on formaldehyde emissions from samples collected from temporary housing units (THUs) was studied. The THUs were supplied by the U.S Federal Emergency Management Administration (FEMA) to families that lost their homes in Louisiana and Mississippi during the Hurricane Katrina and Rita disasters. Based on a previous study 1, 2, four of the composite wood surface materials that dominated contributions to indoor formaldehyde were selected to analyze the effects of temperature and humidity on the emission factors. Humidity equilibration experiments were carried out on two of the samples to determine how long the samples take to equilibrate with the surrounding environmental conditions. Small chamber experiments were then conducted to measure emission factors for the four surface materials at various temperature and humidity conditions. The samples were analyzed for formaldehyde via high performance liquid chromatography. The experiments showed that increases in temperature or humidity contributed to an increase in emission factors. A linear regression model was built using natural log of percentage relative humidity (RH) and inverse of temperature (in K) as predictor variables, and natural log of emission factors as the target variable. The coefficients of both inverse temperature and log relative humidity with log emission factor were found to be statistically significant for all the samples at the 95percent confidence level. This study should assist to retrospectively estimate indoor formaldehyde exposures of occupants of temporary housing units (THUs).