Emission of Formaldehyde By Particleboard: Effect of Ventilation Rate and Loading on Air-Contamination Levels

Dynamic tests for determining the formaldehyde emission behavior of UF-bonded boards involve the measurement of formaldehyde concentration in the air within a vessel which contains a specified board loading L (m2 of board area per m3 of vessel free volume) and is being ventilated at a specified air exchange rate N(hr.-1). Such tests constitute a primary characterization of board emission behavior since they model conditions for air contamination in dwellings containing those boards. Many other board emission tests, e.g., desiccator, perforator, must be regarded as secondary tests since their results cannot a priori be related to use conditions; to be accepted as valid quality control tests, they must first be correlated with primary test results. Existing approaches toward explaining the dependence of formaldehyde concentration upon ventilation rate and loading in a dynamic test are reviewed. Data for three particleboards are fit by a two-parameter equation in which the reciprocal of steady state formaldehyde concentration is linearly related to the ratio of ventilation rate to loading, N/L. According to one interpretation, the intercept of a plot of reciprocal concentration versus N/L is a measure of the equilibrium concentration (Ceq) in the absence of any air exchange, while the slope measures the rate of formaldehyde transport through the board-air interphase in terms of a mass transfer coefficient K. On this basis, reductions in board emission can be accomplished by reducing Ceq, e.g., by stabilizing the resin, and/or by reducing K, e.g., by coating the board surfaces. Examples are given to show how this equation can be used to evaluate the degree of improvement required for a board to meet permissible air contamination levels and for evaluating the utility of a board under various ventilation rate and loading conditions.

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