## 5 Wood-Based Panel Emissions
### Wood Panels Bonded without Adhesive
#### 5.2.1 VOC Emissions from Heat-Treated Softwoods
VOC emissions from untreated heartwood were found to be more than 10 times higher than those from untreated sapwood (413 mg m\({}^{-2}\) h\({}^{-1}\) and 33 mg m\({}^{-2}\) h\({}^{-1}\) respectively). The main compound emitted by untreated heartwood and sapwood was \(\upalpha\)-pinene, with 714 mg m\({}^{-2}\) h\({}^{-1}\) for heartwood and 77 mg m\({}^{-2}\) h\({}^{-1}\) for sapwood. Camphene, \(\upbeta\)-pinene, hexanal, and limonene were also identified as the main compounds in heartwood emissions, with 9 mg m\({}^{-2}\) h\({}^{-1}\), 8 mg m\({}^{-2}\) h\({}^{-1}\), 6 mg m\({}^{-2}\) h\({}^{-1}\), and 5 mg m\({}^{-2}\) h\({}^{-1}\), respectively. For sapwood emissions, hexanal and pentanal represent 51 mg m\({}^{-2}\) h\({}^{-1}\) and 17 mg m\({}^{-2}\) h\({}^{-1}\), respectively. TVOC emissions increased for both heat treatments between 180 \({}^{\circ}\)C and 200 \({}^{\circ}\)C for heartwood and sapwood. Terpene emissions (\(\upalpha\)-pinene, \(\upbeta\)-pinene, camphene, limonene) from heartwood decreased after both types of heat treatment and were lower at 180 \({}^{\circ}\)C than at 200 \({}^{\circ}\)C, except for pineenes, which were higher at 200 \({}^{\circ}\)C for vacuum heat treatment. Sapwood terpen emissions were lower after heat treatment at 180 \({}^{\circ}\)C, but higher after heat treatment at 200 \({}^{\circ}\)C, except for \(\upbeta\)-pinene, whose emissions after heat treatment were all higher. Aldehyde emissions varied from compound to compound. The aldehydes initially emitted (pentanal and hexanal) were emitted in very low quantities, or were no longer emitted (pentanal) after heat treatment. Other aldehydes, such as furfural, crotonaldehyde, and benzaldehyde, appeared after treatment or were emitted in larger quantities, although these remained low (<1 mg m\({}^{-2}\) h\({}^{-1}\)). Other compounds were also released after heat treatment, including alcohols (1-methoxy-2-propanol), ketones (cyclohexanone), and aromatic hydrocarbons (benzene, toluene, and their derivatives), but the quantities emitted were low (<1 mg m\({}^{-2}\) h\({}^{-1}\)). Three Tunisian pine species (_Radiata pine, Pinus pinaster_, and _Pinus halepensis_) were subjected to different heat treatment severities by [PERSON] et al. (2016). Heat treatments were evaluated in terms of sample mass loss: 0% (untreated), 8%, 10%, or 12% mass loss. The three pine species showed similar behavior with regard to VOC emissions. Firstly, the untreated sample emitted significantly more VOCs than the treated samples. The main compounds emitted were hexanal, \(\upbeta\)-pinene, camphene, nonanal, isobornyl acetate, caryophyllene, humulene, and caryophyllene oxide. Most of these VOCs are no longer emitted after heat treatment. However, at heat treatment corresponding to 8% mass loss, some monoterenes such as pineene and terpenyl acetate were still detected, and furfural appeared in the emissions. After the most severe heat treatment (12% mass loss), only acetic acid, due to the thermal degradation of hemicelluloses, vanillin, and guiaacylacetone, the first lignin degradation products, were detected. [PERSON] et al. [147] studied emissions from untreated and treated wood (spruce, Scots pine, and aspen) for 28 days. They showed that TVOC emissions from spruce and Scots pine decreased with heat treatment (from 550 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) to 220 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) and from 2000 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) to 240 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\), respectively). The main emissions from untreated spruce were \(\alpha\)-pinene (40-120 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)), limonene (40-140 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)), and \(\beta\)-pinene (20-66 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)). In treated spruce, acetic acid (17-53 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)), furufural (14-23 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)), and \(\alpha\)-pinene (3-18 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)) were detected in the majority of cases.