## 3 VOCs from Wood-Based Panels and Products  
Wooden products, especially wood-based panels, composites, and engineered wood products, became an environmental issue recently, as these are very likely the major sources of aldehydes (including formaldehyde) and terpen in newly constructed houses [88]. Since the majority of them are used in indoor decoration and furnishing, the indoor air pollution caused by these materials may lead to the \"sick building syndrome\" [44, 89]. In the wood-based panels industry, the trail of VOCs emission actually starts in the forests and continues ultimately into final products, where wooden fibers, particles, strands, or veneers are bonded with diverse chemical compounds and additives [44, 49, 90]. Then, these materials are the crucial components in the consequent furniture production where glues, adhesives, diluents, curing agents, and paints are additionally used [91]. According to the Environmental Protection Agency (EPA) [92], the sources of VOCs emissions include resins, coatings [93], and other types of finishes that can offgas and pollute indoor air [94]. An emissions test by [PERSON] et al. [95] determined that the overall emission rates from wood products with veneered substrates were significantly higher than the overall emission rates from wood products with melamine and vinyl substrates. This fact occurs due to the sealer and acid catalyzed topcoat used as the veneer finish. However, less harmful chemicals are being used due to environmental and health concerns, and the emissions of VOCs from additives, glues, coatings, and polymers are being steadily reduced [96]. Hence, the emission rate depends on the wood species as well as on production factors and boundary conditions, such as drying, hot pressing, storage, etc. [44]. It was shown that the VOCs emitted during wood particle drying mainly consist of terpenes [97]. Thus, terpenes are mostly derived from wood particles, not from glues and resins in wood-based panels production [79]. The study of [PERSON] et al. [86] revealed that in contrast to that, urea-formaldehyde (UF) resin used for medium-density fiberboard (MDF) production had the lowest total VOCs content, while the wood chips had the highest. Comparing the glues used for MDF production, UF resin proved to have the highest emission concentration, while the melamine formaldehyde (MF) adhesive system had a lower one, and polyvinyl acetate (PVAc) had the lowest [25]. MF resin was also used in the study of [PERSON] et al. [81] testing formaldehyde emissions from various raw materials as well as manufactured wood. It was concluded that wood species, as well as processing, are the key factors influencing formaldehyde emission [28, 86, 98]. [PERSON] et al. [81] found six times higher formaldehyde emission from beech than from poplar, oak, or pine (84, 14, 14, and 16 \(\upmu\)g m\({}^{-2}\) h\({}^{-1}\) respectively) and assumed that in processed materials, during two weeks after material manufacturing, a significant decrease in formaldehyde emission can be observed. [PERSON] et al. [89] emphasize the influence of processing parameters on VOCs emissions in larch particleboard (PB) production. The concentration and emission rate of VOCs were significantly affected by hot pressing temperature and time. The increase of temperature leads to an increase of total VOCs emission in the beginning. Then, the concentration of VOCs collapses dramatically within the first 60 min of heat exposure. The higher density, thickness, and resin content of larch PB were considered primary reasons leading to higher terpenes and aldehydes emissions and to a total VOCs increase. A similar trend was observed in case of press time prolonging. This phenomenon is linked to the content of wood extractives in larch. A study of [PERSON] et al. [79] reports on the effect of larch PB density,thickness, and resin content on total VOCs and VOCs emission. Terpenes emission from the material exhibited an increment by adding density and thickness, and it dropped while increasing UF resin content.