Effect of sample conditioning and chamber loading on rate of formaldehyde release from wood products in a desiccator test

Abstract

Several variables may influence the observed rate of formaldehyde (CH 2O) offgassing from wood products in a small static test chamber. We studied the effect of sample conditioning at ≈100% relative humidity and chamber loading (sample size) on CH 2O release rate from particle board (PB) and plywood (PW). Samples of PB and PW were placed in glass desiccators with reservoirs of water at a loading of 21 m 2/m 3 (sample surface area per chamber volume). The rate of CH 2O offgassing from the PB did not change over several weeks under these conditions (0.24 μg/cm 2/day), but the overall release rate from the PW decreased after 8 days. In another experiment, the loading of the desiccator had a major effect on the rate of CH 2O offgassing from PB over a loading range of 1 to 42 m 2/m 3. The same phenomenon was observed with different loadings of PW. The inverse of the observed release rate varied linearly with the chamber loading of PB or PW. At a loading which may be encountered in a house (0.25 m 2/m 3), the release rate coefficient for PB calculated from the above inverse relation was 22-fold higher than that measured at a more conventional test load of 21 m 2/m 3. These results indicate that great care should be exercised when using desiccator tests for assessing and comparing the potential strength of materials as sources of CH 2O in the indoor environment.