## 3 Volatile Organic Compounds Emitted from WBPs
### Aldehydes, Carboxylic Acids, and Ketones
(2002) [87] compared air-dried and heat-treated pine wood (_Pinus sylvestris_) and found that terpene emissions were higher in air-dried samples, which exhibited a lower variety and percentage of aldehydes. In contrast, heat-treated samples showed significant differences in their emission profiles. The major compounds emitted in heat-treated pine were acetic acid (23.91%), fur furural (28.37%), and acetone (7.34%), which were absent from air-dried pine samples as they occur through thermal degradation. Other carbonyl compounds identified were hydroxyacetone, hexanal, octanal, nonanal, decanal, benzaldehyde, and 5-methylfurfural. Overall, aldehydes contributed 34.54% to the total VOC emissions from heat-treated wood, followed by carboxylic acids and their esters (30.64%) and ketones (16.20%). Terpene emissions accounted for only 9.69%, contrasting to the 77.03% emitted from air-dried pine. Similarly, a study from [PERSON] et al. (2018) [65], which compared untreated pine and heat-treated southern yellow pine (_Pinus_ spp. ), concluded that a higher percentage of carbonyl emissions occurred in heat-treated samples. In 2010, benzoic acid was also reported in heat-treated pine (_Pinus sylvestris_), while the hardwood aspen (_Populus tremula_) emitted benzoic, propanoic and hexanoic acids from both air-dried and heat-treated samples. Furthermore, the emission rates of organic acids and aldehydes were shown to remain constant throughout 4 weeks, regardless of wood type (softwood or hardwood) or drying treatment (air-dried or heat treatment) [66]. [PERSON] et al. (2000) [94] studied aldehyde emissions from PBs and MDFs produced with wood from different species. The study identified pentanal, hexanal, heptanal, benzaldehyde, octanal, _trans_-oct-2-enal, and nonanal as the most predominant aldehydes in both products. Formaldehyde was not detected by the GC-MS method used, due to being too volatile. Overall, MDF emissions were substantially lower than PB emissions, except for panels made from southern pine. Hexanal was the most significant contributor to total VOC emissions across most samples, namely Douglas fir PBs (41%), other pine PBs (44%), southern pine PBs (48%), other pine MDFs (47%), southern pine MDFs (58%), other PBs  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Wood** & **Volatile Carbonyl Compounds Emitted \({}^{*}\)** & **References** \\ \hline \multirow{8}{*}{\ \begin{tabular}{} \end{tabular}  } & \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & formaldehyde, acetaldehyde, propanal, butanal, pentanal, hexanal, octanal,  
with undetermined wood (68%) and hardwood PBs (80%). Aldehyde emissions were higher than non-aldehyde emissions in all panels, except for Douglas fir PBs (49%), hardwood MDFs (40%), and other MDFs with undetermined wood (16%). In a study from [PERSON] et al. (2020) [77], emissions from PB and laminated PB--both produced with the same wood particles--were analyzed and several volatile groups were identified in both samples. Among them were carbonyl compounds such as acetaldehyde and straight chained aldehydes ranging from C\({}_{6}\) to C\({}_{11}\), methylal (dimethoxymethane), acetone, ethyl acetate, methyl methacrylate, and acetic acid esters. The use of additives, such as flame retardants, has also been reported to influence the VOCs emitted from wood and WBPs. In 2023, [PERSON] et al. [95] studied the effect of ammonium sulphate, an acid-based flame retardant, on lightweight insulation fiberboard. Results showed a noticeable increase in the emissions of acetic acid and furfural when compared to panels without the additive. More recently, [PERSON] et al. (2025) [96] compared emissions from untreated and flame retardant-treated spruce wood (_Picea abies_) under thermal loading. The findings indicated that furfural was the main emission in flame retardant-treated spruce.