Dissertations in Forestry and Natural Sciences

Discussion
findings mirror the results obtained in study II, the material
they used is not fully comparable to WPCs. Particleboards and
wood-based panels sometimes contain formaldehyde-based
resins that can dramatically alter the emission characteristics.
This could also be observed in their results; the emissions of
formaldehyde were over ten times higher than those of
acetaldehyde after 28 days. Contrasting results were obtained in
study II: the emissions of acetaldehyde were approximately 3
times higher than those of formaldehyde after 41 days.
Cyclohexene is an irritant to humans and it is considered to
be at least partly responsible for the unpleasant odor of WPCs.
Cyclohexene and its derivatives are present in the essential oils
of multiple wood species (Amoore and Hautala 1983,
Chowdhury et al. 2008, Peters et al. 2008). The emissions of
cyclohexene remained stable during the first 13 days of the trial.
However, the detected emissions nearly tripled on day 16 and
remained at that level for the rest of the trial. The emissions of
cyclohexene from WPCs have not been studied previously, so
there is no supporting information for this finding. There are
several reasons to account for the unexpected change on day 16.
For example, the unique release kinetics of cyclohexene can
explain the result. In addition, due to the extremely high
sensitivity of PTR-TOF-MS, one cannot completely rule out the
possibility that some minor loosening or movements of the
Kapton ® tape may have been responsible for the change in the
emissions. However, this is unlikely because one would have
expected to detect similar changes in the emission rates of other
VOCs.
Furan and guaiacol have similar odor characteristics and
they are formed in similar processes. They have odors
reminiscent of burning wood, and both are formed during the
thermal treatment. (Goldstein 2002, Greenberg et al. 2006,
Aigner et al. 2009) Furan has been classified as a possible
carcinogen with a high odor threshold (Bakhiya and Appel 2010)
whereas guaiacol has a very low odor threshold with no direct
health effects. The detected emission rates for furan were low
throughout the trial, and there were no major changes observed
Dissertations in Forestry and Natural Sciences No 222 105