The Effects of Temperature and Humidity on Formaldehyde Emission from UF-Bonded Boards: A Literature Critique

An analysis has been conducted on available data related to temperature and humidity effects on formaldehyde concentrations that are produced by emission from particleboard and hardwood plywood paneling. Temperature changes are described by an exponential relation while a linear relation suffices for humidity effects. Large variations exist in the results from different investigators on different boards for the exponential temperature coefficients (-5620? to -12,480?K-l) and for the linear humidity coefficients (0.005 percent to 0.038 percent-1). The variations appear to be caused by experimental errors, procedural differences between laboratories, board to board differences, and board aging. Statistical treatment of all chamber test data as a composite set (normalized to unity at 25?C) yields a composite temperature coefficient of -8930?K-l, with a 95 percent confidence interval from -8390? to -9470?K-l (? 6 percent relative error). Using this composite, calculated correction factors, (25?C)/c(T), varies from 4.89 at 10?C to 0.152 at 45?C. The statistical analysis also indicates that significant board to board and laboratory to laboratory variations occurred. Assuming this composite coefficient is indeed valid for a particular board or dwelling, it can be used to make temperature corrections to standard temperature with, for example, relative errors (95 percent confidence) in correction factors being ? 7 percent for a ? 10?C temperature difference. In the absence of knowledge about the specific applicability of a particular temperature coefficient, however, temperature corrections should probably be restricted to a 5?C range, except for general engineering or planning purposes. A similar composite analysis of all the humidity data (normalized to unity at 50 percent relative humidity (RH)) yields a composite a of 0.0195 percent-l with a 95 percent confidence interval from 0.014 to 0.025 (? 28 percent relative error). The corresponding correction factors, c(50 percent)/c(RH), vary from 2.41 at 20 percent RH to 0.56 at 90 percent RH. Very large variations between investigators and between boards lead to poor confidence in such composite universal humidity correction factors however, and no clear recommendation can be made regarding correction factors to convert formaldehyde concentrations to a standard humidity. Small humidity changes (~10 percent RH) however, probably can be neglected since they may be masked by rather minor temperature changes (? l? to 2?C). Much more information is needed to clarify the reasons for the large variability and to increase confidence in temperature and humidity correction factors.

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