## 2 Materials and Methods
### Determination of VOCs by SPME-GC-TOF-MS Analysis  
HS-SPME was performed to analyze and compare volatile organic compounds (VOCs) emitted from different board samples, summarized in Table 1. Prior to analysis, the conditioned (RH 65 \(\pm\) 5%, 20 \(\pm\) 2 \({}^{\circ}\)C) board samples were cut to the rectangular specimens with an approximate area of 7 \(\times\) 7 mm\({}^{2}\) from different board sample parts to represent all the board sample. The original thickness of the board specimens was maintained to clarify the impact of board (1) thickness, (2) density, and (3) lamination. The cut board  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **Lignocellulosic** & **Density**, **kg m\({}^{-3}\)** & **Thickness, mm** & **Pressing T, \({}^{\circ}\)C** & **Pressing \(\tau\), min** & **Overlaying** \\ \hline HS 800-6 & Hemp shives & 800 & 6 & 220 & 10 & – \\ HS 800-6L & Hemp shives & 800 & 6 & 220 & 10 & + \\ HS 800-12 & Hemp shives & 800 & 12 & 210 & 15 & – \\ HS 1200 & Hemp shives & 1200 & 6 & 175 & 16 & – \\ WS 800-6 & Wheat straw & 800 & 6 & 220 & 15 & – \\ WS 800-6L & Wheat straw & 800 & 6 & 220 & 15 & + \\ WS 800-12 & Wheat straw & 800 & 12 & 205 & 18 & – \\ WS 1200 & Wheat straw & 1200 & 6 & 160 & 12 & – \\ GA 700 & Grey alder & 700 & 6 & 180 & 16 & – \\ GA 1300 & Grey alder & 1300 & 6 & 150 & 16 & – \\ B 700 & Birch & 700 & 6 & 180 & 16 & – \\ B 1300 & Birch & 1300 & 6 & 160 & 16 & – \\ SA-PB & Birch & 800 & 15 & 226 & 9.5 & – \\ Commercial PB & Softwood & 650 & 12 & 235–220 & 1 & – \\ \hline \hline \end{tabular}
\end{table}
Table 1: Designation and fabrication conditions of board samples provided for VOCs analysis.  
specimens were placed separately in desiccators (Figure 1) and weighed at 2.1 \(\pm\) 0.05 g for HS-SPME performance after days 1, 14, and 28. Triplicate desiccators with precisely weighed specimens were prepared per board sample.  
All samples were analyzed on a gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) LECO Pegasus 4D system, consisting of an Agilent 7890A GC system and a Gerstel multipurpose sampler MPS (Gerstel GmbH, Mulheim an der Ruhr, Germany) coupled with a high-speed TOF-MS detector (LECO, St. Joseph, MI, USA). Sample separation was achieved in a BPX-5 column (30 m, 0.25 mm i.d., 0.25 \(\upmu\)m film thickness) (SGE Analytical Science, Melbourn, Australia). The following conditions were applied: the oven temperature started at 30 \({}^{\circ}\)C (hold 5 min) and was ramped to 150 \({}^{\circ}\)C at a 7 \({}^{\circ}\)C/min rate until 300 \({}^{\circ}\)C at 20 \({}^{\circ}\)C/min; the transfer line and ion source temperature was set to 250 \({}^{\circ}\)C; the TOF-MS acquisition rate was 10 spectra/s; the mass range was 30-550 \(m/z\). Data were collected by ChromaTOF software v.4.22 (LECO) after a solvent peak delay of 30 s.  
SPME was performed with a DVB/CAR/PDMS fiber at an equilibration temperature of 40 \({}^{\circ}\)C. Samples were equilibrated for 30 min, and then the fiber was exposed for extraction for an additional 30 min. Samples were introduced in the splitless mode in a PTV injector operated at 150 \({}^{\circ}\)C and then ramped to 250 \({}^{\circ}\)C at 12 \({}^{\circ}\)C/s. Helium was used as a carrier gas at a constant flow of 1 mL/min and desorption time of 300 s.  
Volatile compounds were identified by comparing their mass spectra with the Adams, NIST, MainLib, and Replib mass spectral libraries. Retention indexes (RI\({}_{\text{exp}}\)) were calculated using the retention times of C7-C30 n-alkanes series and further compared with previously published data in the literature (RI\({}_{\text{lit}}\)), when available. The results were expressed as GC peak area arbitrary units \(\times 10^{7}\) (further abbreviated as AU) and percentage (%) of the total GC peak area.