Formaldehyde emission from particleboard and plywood paneling: measurement, mechanism, and product standards

A number of commercial panel products, primarily particleboard and hardwood plywood, were tested for their formaldehyde emission behavior using desiccator, perforator, and dynamic chamber methods. The results were analyzed in terms of the source of formaldehyde observed in the tests (free vs. hydrolytically produced) and the potential utility of the testa as product standards for boards in mobile homes. A greater than tenfold range of formaldehyde emissions was observed, well above and below levels that would be acceptable for proposed mobile home air levels. It was demonstrated that observed maxima in dynamic concentration-time curves were due to depletion of initial board free formaldehyde (as measured by perforator) and emission of hydrolytically produced formaldehyde at a lower rate. The 2hour desiccator test measures less than 0.5 percent of the boards’ initial free formaldehyde content and therefore does not necessarily reflect resin hydrolytic stability. Approximate linear correlations were observed between desiccator or perforator values and dynamic chamber concentrations. However, large deviations occurred from the linear regressions. It was concluded that without large safety factors and/or much more testing to clarify those deviations neither the desiccator nor perforator test could provide reliable product standards for board emission. Indoor air-pollution by formaldehyde that is emitted from adhesively bonded wood products has been a major concern in the forest products industry in recent years. A very important facet of the overall problem has been the development and evaluation of methods to characterize the formaldehyde off-gassing tendency of materials such as particleboard, hardwood plywood paneling, and medium-density fiberboard (MDF). There were two primary goals in the methods development effort. First, a simple, reproducible test was desired that could be reliably performed in board manufacturers’ laboratories – i.e., a quality control test. For this purpose it was essential that a one-to-one correlation exist between such quality control test values for boards and the consequent air contamination levels that would be produced in a dwelling made with those same boards. Second, as a consequence of meeting the first goal it was expected that valid product standards could be established for boards – i.e., maximum quality control test values that would prevent specific air-contamination levels from being exceeded. Efforts at the Forest Products Laboratory (FPL) during the past several years have been directed toward these goals. We have examined several potential quality control tests, with emphasis upon the desiccator and perforator methods (7). The desiccator test was emphasized because it appeared likely to be adopted as the industry quality control method in the United States (2, 8). The perforator test was studied because it is widely used in Europe as a quality control test and because it is believed to measure a very important board emission characteristic, the board‘s free’ formaldehyde content