Up to twenty-three OSB products from Canada and US were tested for their VOCs. The results collected indicated that OSB panels emit at a very low level, in the order of few parts per billion (ppbs). The emission of monoterpenes such as alpha and beta-pinenes, camphene, carene and limonene from all of the tested OSB panels were very minor when they were present. In order to put in perspective the OSB panels emissions, a few tests were conducted on panels bonded with urea-formaldehyde resin and MDI. Results indicated that more VOCs and formaldehyde emit from the UF bonded panels compared to the PF or MDI bonded OSB panels. The UF emitted formaldehyde remains however far less than the 0.3 ppm recommended formaldehyde emission level by the new Composite Panel Association (CPA). VOCs observed from UF bonded panels consist mainly of monoterpenes which are naturally emitted from the softwood furnish used for the particleboard manufacturing and of formaldehyde at a level.
The evaluation of the long term effect on OSB panel emissions showed that all emitted individual chemicals (IVOC) and total emitted volatile organic chemicals (TVOC) decreased with exposure time. However, the two-week long term exposure period was not long enough in most cases to reach a 0 percent emission level. The positive aspect of these results is related to the fact that during the two to three-week delivery period to the client, the emissions are reduced by up to 90% of their initial first day value.
During the investigation of the effect of some key processing parameters on the final product emission characteristics, the drying temperature of the furnish and its moisture content as well as the pressing time and temperature and the resin contents were evaluated. Three OSB mills supplied the furnish (green and dried wafers) and the panel products. Results indicated that emissions from the wafers decrease in most cases when dried at high temperatures compared to the air-dried wafers for a given moisture content. Because the furnish composition (percentage of softwood compared to hardwood) can be different from one mill to another, one can anticipate a certain impact on the furnish emission characteristics and thus on the OSB products emissions. However, after a few days of exposure, the three OSB panels showed almost the same emission level.
The investigated furnish drying conditions showed very clearly that the drying temperature plays an important role on its emissions. Results indicated a gradual reduction of the TVOC, the emitted aldehydes and ketones when a furnish, dried at different temperatures, i.e., from ambient to high temperatures, is exposed in the environmental chamber. Also, the combined effect of moisture content and drying temperatures on furnish emissions showed, as expected, an increase of the detected TVOC as the moisture content and the drying temperature increase. This result support the fact that air-dried furnish should emit more than a furnish dried at high temperature when exposed in the environmental chamber conditions. However, at very high drying temperature, the furnish starts to degrade and an increase of the emission level could be observed.
Results acquired to date indicated that resin contents, pressing times and temperature values selected for the 27 different OSB panel processing conditions, were not different enough to have a significant impact on the composite panels emission levels. The total emitted chemicals (TVOC.) from the 27 OSB panels compare very well to the 23 industrial TVOC values. This result indicates that it should be necessary to find other combination values for the resin contents, the pressing times and the temperatures, quite different from their corresponding industrial values to better evaluate their impact on the resulting panel VOC emission patterns, and this should be done without affecting the product quality. The acquisition of such data will certainly have less interest for the wood composite panel industry if the manufacturing cost has changed but it will help for a better understanding of these parameters impact on the product emission characteristics.
One of the objectives of this project was to develop a quality control monitoring guideline. The twenty-three (23) North American OSB products tested in this project showed that the maximum TVOC observed was less than 0.04 parts per million (ppm), and the maximum detected formaldehyde less than 0.014 parts per million (ppm), which represents one twentieth of the 0.3 ppm of formaldehyde recommended value by the CPA for the particleboard and medium density fiberboard (MDF) products. Based on these results, we have recommended a voluntary, twice per year, VOC emission quality control for each OSB product to the OSB industry. A detailed procedure for sample collection, preparation and shipping to the Forintek Laboratory at Ste-Foy is described. The sample conditioning, emission collection and characterization procedures will be the same as those described in this report.