## 3 Results and Discussion  
In this work, hemp shives were subjected to simple chemical treatments, and their VOCs were analyzed and compared to untreated hemp shives and spruce strands. Thirteen key volatile organic compounds including carbonyl compounds, alkanes, aromatic hydrocarbons and terpen were collected from untreated and chemically treated hemp shives by HS-SPME GC-MS. Target compounds (Table 2) were selected based on a list published in ISO 16000-6 (Annex A) dealing with the building products' VOC emissions in indoor air [31]. In general, a higher number of VOCs, as well as higher detector responses, were observed in spruce strands compared to untreated hemp (Figure 2), especially in case of Pentanal, Hexanal, Furfural and Benzaldehyde. This observation corresponds with an expected higher content of extractives in spruce wood [14; 17]. Small test chambers were used to simulate typical interior room conditions where partial changes of air volume were taking place continuously [15]. After 14 days of storage in desiccators with a constant air flow, a slight decrease in intensity signal of above mentioned compounds was observed. A pentanal increase was reported only after sodium bicarbonate treatment and it was later decreasing during storage. Together with more important aldehyde-hexanal, it is known as a product of unsaturated fatty acids oxidation [14]. Both compounds have been identified as causing unpleasant, irritating odors [32] and are known to cause off-flavors in low concentrations in paper [33]. Hexanal, described as grassy [34], kept its initial value after sodium bicarbonate treatment. It was then increasing in all other materials (Figure 3) during storage (especially in case of untreated hemp). Both materials in untreated forms emitted similar amounts of acetic acid. Meanwhile acidic treatments enhanced the emission of this compound; sodium bicarbonate treatment led to its inhibition. Unpleasantly smelling butanoic acid was not present in untreated hemp as well as in sodium bicarbonate treated samples (signal below limit of detection--LOD), while the acid treatment significantly increased its abundance. Comparing the untreated and sodium bicarbonate treated hemp shive, aldehyde (hexanal and octanal) emissions lowering effect of sodium bicarbonate was observed, while the emission of other compounds (especially terpen) rose. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c c c c} \hline \hline  & \multicolumn{11}{c}{**SAMILES \& \& SAMPLING DAYS**} \\ \cline{2-13}
**COMPOUND** & \multicolumn{4}{c}{**S**} & \multicolumn{4}{c}{**H**} & \multicolumn{4}{c}{**H\({}_{\rm A}\)**}  
A wide variety of terpenes (such as alpha-pinene, beta-pinene, camphene, 3-carene and limonene) was observed (Figure 4) in both samples (spruce and hemp). Nevertheless, it should be noted that even higher responses of terpen in the case of hemp were still significantly lower than those measured in the spruce samples. Moreover the amount was decreasing with time. Basic chemometric data evaluation using PCA clearly demonstrated the separation of spruce strands samples from all hemp samples. It was caused by higher relative abundance of characteristic spruce wood volatiles, alpha and beta-pinene. These findings confirmed a difference in released VOCs between untreated spruce strands and untreated hemp shives, showing that untreated hemp shives can be regarded as a safe construction material for indoor air quality. Figure 2: Selected VOC emissions from spruce wood and untreated hemp (day 1, 3, 7, 14; detector response for unique mass) (**a**): untreated hemp shive; (**b**): spruce strands. To further investigate differences among hemp treatments, partial least square-discriminant analysis (PLS-DA) was performed. No separation was observed according to the duration of storage, while samples were separated based on chemical solutions treatment (Figure 5). In the case of hemp, both acid treated samples formed one group, mainly due to higher abundance of furfural (Figure 6).