## 5 Wood-Based Panel Emissions
### Wood Panels Bonded without Adhesive
#### 5.2.2 VOC Emissions from Heat-Treated Hardwoods  
[PERSON] et al. [147] compared emissions from poplar (_Populus tremula_) before and after heat treatment at 190 \({}^{\circ}\)C and found that poplar before heat treatment emitted more VOCs than after (513 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) vs. 109 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\)). In addition, they observed that the VOCs most emitted before and after treatment were carbonyl compounds. Before treatment, emissions were mainly represented by hexanal, acetic acid, and pentanal, with respective emission rates of 330 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\), 54 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\), and 46 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\). In contrast, after heat treatment, acetic acid and furufural were the major compounds, with emission rates of 88 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) and 77 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\), respectively. [PERSON] and [PERSON] [149] studied VOC emissions from untreated poplar and poplar heat treated at 180 \({}^{\circ}\)C or 200 \({}^{\circ}\)C, demonstrating in particular that VOC emissions from poplar increased with heat treatment and with treatment temperature. Indeed, 3 h after heat treatment, poplar emissions were linked to 31 \(\upmu\)g m\({}^{-3}\), 73 \(\upmu\)g m\({}^{-3}\), and 178 \(\upmu\)g m\({}^{-3}\) concentration in the emission chamber for untreated wood, wood treated at 180 \({}^{\circ}\)C, and wood treated at 200 \({}^{\circ}\)C, respectively. They observed a strong influence of treatment temperature on furufural and phenol emissions in particular, which are typical compounds of hemicellulose and lignin degradation. VOC emissions from heat-treated poplar were analyzed by [PERSON] et al. [145]. For this, the authors compared untreated poplar with poplar treated at 160 \({}^{\circ}\)C, 180 \({}^{\circ}\)C, 200 \({}^{\circ}\)C, or 220 \({}^{\circ}\)C. Like [PERSON] and [PERSON] [149], they found that VOC emissions were higher after wood treatment. [PERSON] et al. [150] classified VOC emissions by compound type (alcohols, aldehydes, furans, aromatic compounds, esters, and alkanes). Aldehydes were the compounds emitted most at all treatment temperatures (except 220 \({}^{\circ}\)C), with a maximum contribution of 83% at 180 \({}^{\circ}\)C. For untreated poplar, aldehyde emissions accounted for 30% of total emissions,with decanal (10% of total VOC emissions), 2-nonenal (10% of total VOC emissions), and nonanal (5% of total VOC emissions) as the main compounds. However, the main compound emitted by untreated poplar was a carboxylic acid: oxalic acid (32% of total VOC emissions). Aromatic compounds were the second most emitted by untreated poplar, along with naphthalene (6% of total VOC emissions) and methylnaphthalene (12% of total VOC emissions). At 160 \({}^{\circ}\)C and 180 \({}^{\circ}\)C, aldehydes remained the dominant compounds, accounting for over 70% of emissions at 160 \({}^{\circ}\)C and over 80% at 180 \({}^{\circ}\)C. Indeed, 2-nonenal, furfural, and decanal represented, respectively, 40%, 4%, and 11% of total VOC emissions at 160 \({}^{\circ}\)C and 43%, 17%, and 5% of total VOC emissions at 180 \({}^{\circ}\)C. At 200 \({}^{\circ}\)C, furfural became the majority aldehyde, accounting for 27% of total VOC emissions. However, at 200 \({}^{\circ}\)C, phenol appeared and was emitted in greater quantities than furfural, accounting for 29% of total VOC emissions. Emissions of aromatic compounds generally increased with temperature, reaching 30% of total VOC emissions at 220 \({}^{\circ}\)C, with phenol (16% of total VOC emissions), methylnaphthalene (10% of total VOC emissions), and naphthalene (4% of total VOC emissions). Esters appeared at 180 \({}^{\circ}\)C and increased with temperature, accounting for 13% of total emissions at 220 \({}^{\circ}\)C, with methyl benzoate (9% of total VOC emissions) the main compound at 220 \({}^{\circ}\)C.  
[PERSON] et al.