Effect of ambient environmental factors on indoor formaldehyde levels

The effect of ambient (outdoor) environmental parameters on formaldehyde levels in a temperature controlled urea-formaldehyde foam-insulated (UFFI) house and a mobile home was investigated over a 9-month period (July–March). Strong correlations between formaldehyde levels, solar radiation, ambient temperatures, inside/outside temperature differences and water vapor pressure were observed in the UFFI house and in the mobile home. Stepwise regression revealed a significant independent effect of solar radiation values on indoor formaldehyde levels in the UFFI house but not in the mobile home. Stepwise regression revealed no significant independent effect of the other environmental variables evaluated. The independent effect of solar radiation on formaldehyde levels in the UFFI house indicates that solar radiation can have a significant effect on formaldehyde concentrations, and this effect may explain anomolous results in whole house source interaction studies.