## 4 Methodologies Used for the Analysis of VOCs in WBPs  
### International Standards  
The ISO 16000 series addresses the assessment of indoor air quality and is divided into several parts. Among these, a select number specify standardized methodologies for the determination of VOCs in indoor air.  
The active sampling method described in ISO 16000-3 [110] enables the determination of formaldehyde and 12 other volatile carbonyl compounds in the air inside a test chamber and in indoor air. The air is drawn through a silica gel cartridge coated with 2,4-dinitrophenylhydrazine (DNPH) reagent, where the carbonyl compounds will form stable derivatives with DNPH. The resulting derivatives are analyzed by high-performance liquid chromatography (HPLC) with ultraviolet detection or diode array detection (DAD). This method can be used for short-term (5 min to an hour) and long-term (1 h to 24 h) air sampling, and the results are usually expressed in parts per million, ppm.  
In ISO 16000-6 [111], the determination of VOCs emitted from building materials and other products used in indoor environments is specified. Sampled air from an emission test chamber or cell is drawn through one or more Tenax TA(r) sorbent tubes to capture the analytes. By means of thermal desorption, the captured VOCs are analyzed by gas chromatography (GC) using a flame ionization detector and/or a mass spectrometry (MS) detector. The concentration of the identified individual VOCs is expressed in ug\(\cdot\)m\({}^{-3}\).  
ISO 16000-9 [112] specifies a method for determining the area-specific emission rate of VOCs from building products and furnishings using an emission test chamber. To determine the area-specific emission rate by the concentration of VOCs in the air, the test must be conducted in an emission test chamber at a constant temperature of 23 \({}^{\circ}\)C, relative humidity of 50% and area-specific air flow rate. Air sampling shall occur at 72 h and 28 days after the start of the test. The air sampling process and the analytical method for the determination of VOCs are the same as described in ISO 16000-6. The concentration of individual compounds and/or total VOCs is expressed in ug\(\cdot\)m\({}^{-3}\).  
Regarding emissions of regulated hazardous substances from construction products into indoor air, the EN 16516 [42] describes a horizontal reference method based on the test chamber which allows the determination of VOCs, very volatile carbonyl compounds and ammonia. Chamber conditions are the same as those described in ISO 16000-9. The air sampling and analysis of VOCs is performed in a similar manner to that described in ISO 16000-6, while the determination of formaldehyde, acetaldehyde, propanal, butanal and acetone occurs similarly to ISO 16000-3.  
Although these methods use a test chamber, which allows an accurate representation of an indoor environment during sampling, they are also associated with high costs and often long sampling times. For example, ISO 16000-9 defines a 28-day sampling period. This extended duration can pose a challenge for routine internal emissions monitoring in the WBP industry.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Wood** & **Other Volatile Compounds Emitted \({}^{*}\)** & **References** \\ \hline \multirow{4}{*}{VOCs} & Oak & methanol, ethanol, propan-2-ol, 2-penthylfuran & [48, 91] \\  & (_Quercus robur_) & & \\ \cline{2-4}  & Beech & & \\  & (_Fagus sylvatica_) & & \\ \cline{2-4}  & Ash & & \\  & (_Franxinus exexelsior_) & methanol, ethanol, 2-penthylfuran & [48, 92] \\ \hline \hline \end{tabular}  
* The order in which these compounds occur is not indicative of the reported emitted amounts.  
\end{table}
Table 8: _Cont._