The Impact of Relative Humidity on the Emission Behaviour of Formaldehyde in Building Materials

Relative humidity (RH) is one of the main environmental factors affecting the emission behaviours of formaldehyde from building materials. Meanwhile, the initial emittable concentration (C_m,0) is proved to be the most sensitive key parameter to the emission behaviours. However, there is no report on the relationship between RH and C_m,0. In this paper, C_m,0 of formaldehyde from a type of medium density fiberboard in RH range of 20%-85% were tested by the ventilated C-history method. Experimental results show that C_m,0 increased by 10 times when RH rising from 20% to 85%. A linear relationship between ln(C_m,0) and RH is obtained based on the experimental results. A correlation characterizing the association of emission rate and RH is also derived. With the correlations, the C_m,0 or emission rate different from test RH conditions can be conveniently obtained. This study should be useful for predicting the emission characteristics under varied RH conditions.