## 3 VOCs from Wood-Based Panels and Products
As the heat exposure time was extended during manufacture, the total VOC from all other PB samples produced under different manufacture conditions decreased. A study from [PERSON] et al. [78] focused on the emissions of terpen from PB and MDF samples from the North American production. Among the PB samples, the predominant compounds were pinenes, camphene, \(\Delta\)3-carene, p-cymene, limonene, and borneol--the VOCs typical for wood (see Table 1). It was also proved that the terpenes emission from PB and MDF decreases within 4 days in a test chamber by 20 to 80%. An interesting observation was made while comparing PB and MDF produced from the same raw material. In most PB, 3-cerene and pinenes were present, while most of these compounds were absent in the MDFs. This is due to the processing of wood particles that are converted to fibers using a pulping process. The temperature in the pressurized refiner is generally held between 160 and 185 \({}^{\circ}\)C. This high-temperature process may drive terpen from the material, resulting in lower emissions by the final product. According to this explanation, the terpenes with lower boiling points, such as \(\alpha\)- and \(\beta\)-pinene (boiling points of 155 and 165 \({}^{\circ}\)C respectively), were completely absent from the MDF emissions, whereas the higher boiling terpen, such as limonene (boiling point of 176 \({}^{\circ}\)C), were present only in some of the samples. Then, [PERSON] et al. [89] presented acetic acid-butyl ester, \(\alpha\)-pinene, and benzene as the main VOCs emitting from PB, especially after being hot-pressed. Terpenes and aldehydes are the main volatiles emitted from oriented strand boards (OSBs) [73], specifically pentanal and hexanal, which are released during the drying of hardwood flakes for OSBs. [PERSON] et al. [99] and [PERSON] et al. [100] stated that these and other aldehydes are oxidation products of wood components formed during wood drying operations. The presence of hexanal is facilitated by drying at elevated temperature. The emission of hexanal lowers with time while the boards are in an air-conditioned environment [101]. A specific category of wooden products are wooden floors. The oak parquets as a frequent building material were considered risky in terms of VOCs emission, especially while being used as a top layer of flooring systems using floor heating. As described by [PERSON] [16], heating may emphasize the VOCs emission. Parquet samples are expected to be VOCs emitters due to the general degradation of wood, wood volatile compounds, and volatile compounds from the coatings--as well as eventually from the adhesives used to produce a stable multilayer parquet. For example, nonanal comes from the autoxidation of the fatty acids contained in wood. Nonanal is a growth factor for wood-rotting fungi [102]. Although many aldehydes are emitted from wood flooring as a consequence of the autoxidation of fatty acids contained in wood, there is increasing evidence that the chemical reaction between ozone and terpen such as d-limonene or alpha pinene can produce a number of different aldehydes [103]. It is worth noticing in the case of multilayer wood flooring that plywood had been mentioned as a source of \(\alpha\)-pinene, nonanal, octanal, pentanal, and hexanal as a predominant compound [88; 99; 104]. The plywood subfloor, composed of softwood species, had in general comparable emissions with softwood PBs [78].