The effect of humidity on formaldehyde emission parameters of a medium-density fiberboard: Experimental observations and correlations

Initial emittable concentration (C0), diffusion coefficient (Dm) and partition coefficient (K) are the three key emission parameters determining formaldehyde emissions from “dry” building materials. Previous studies of humidity effect on formaldehyde emissions were mainly focused on the analysis of steady-state emission rates or concentrations, whereas humidity effects on emission parameters were seldom discussed. In this study, we measured formaldehyde emissions of a medium-density fiberboard in a dynamic small-scale environmental chamber at the relative humidity (RH) of 20%, 30%, 50% and 80%, respectively. Emission parameters were estimated and the effects of humidity were analyzed. C0 was the most sensitive parameter influenced by humidity, which increased 2.97-fold when RH changed from 20% to 80%. Empirical positive linear relations between C0 and RH, C0 and absolute humidity (AH) were identified. Differences of Dm and K between each humidity scenarios were within 11% and 17%, suggesting the negligible impacts of humidity on them. Moreover, the reversible and simultaneous responses of formaldehyde emissions to humidity changes were exhibited in experiments. Possible mechanisms of humidity effect on formaldehyde emission were hydrolysis of resins or polymers and adsorption competitions between formaldehyde and water molecules. The conclusions and empirical relations obtained in this study would be useful in understanding emission parameters at different humidity conditions.