## 4 Discussion
### Volatile Compounds of the Nicotine-Free Inhalator
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**No**} & \multirow{2}{*}{**Compound**} & **CAS** & **Vapor Samples** & **RD\({}_{\text{8}}\)\({}^{1}\)** & **Sensory** & **DNEL \({}^{3}\)** & **OSHA FEL TWA \({}^{4}\)** \\  & & **Number** & **Mean Conc. (ppm)** & **(ppm)** & **(ppm)** & **(ppm)** \\ \hline
1 & Formaldehyde & 50-00-0 & 0.06 \({}^{5}\) & 4 & 0.12 & 7.43 & 0.75 \\
2 & Acetaldehyde & 75-07-0 & 0.08 \({}^{5}\) & 2845 & 85.4 & n.d. & 200 \\
3 & Propionaldehyde & 123-38-6 & 0.05 \({}^{5}\) & 2078 & 62.3 & 2.60 & n.d. \\
4 & Butylaldehyde & 123-72-8 & 0.08 \({}^{5}\) & 1015 & 30.5 & n.d. & n.d. \\
5 & Isovaleraldehyde & 590-86-3 & 0.07 \({}^{5}\) & 757 & 22.7 & n.d. & n.d. \\
6 & Valeraldehyde & 110-62-3 & 0.10 \({}^{5}\) & 1121 & 33.6 & n.d. & n.d. \\
7 & Acrolein & 107-02-8 & 0.06 \({}^{5}\) & 1.6 & 0.05 & 0.09 & 0.1 \\
8 & Acetone & 67-64-1 & 0.06 \({}^{5}\) & 23,480 & 704 & 517 & 1000 \\
9 & Crotonaldehyde & 123-73-9 & 0.08 \({}^{5}\) & 3.53 & 0.10 & 0.11 & 2 \\
10 & Benzaldehyde & 100-52-7 & 0.11 \({}^{5}\) & 333 & 10.0 & 2.29 & n.d. \\
11 & Methyl ethyl ketone & 78-93-3 & 0.2080 \(\pm\) 0.0068 & 900 & 270 & 206 & 200 \\
12 & Methyl Isobutyl & 108-10-1 & 0.0001 \({}^{5}\) & 3195 & 95.9 & 20.6 & 100 \\
13 & Butyl acetate & 123-86-4 & 0.0001 \({}^{5}\) & 730 & 21.9 & 64.1 & 150 \\
14 & Isobutyl alcohol & 78-83-1 & 0.0001 \({}^{5}\) & 1818 & 54.5 & n.d. & 100 \\
15 & Benzene & 71-43-2 & 0.0012 \({}^{5}\) & n.d. & - & n.d. & 1 \\
16 & Toluene & 108-88-3 & 0.0609 \(\pm\) 0.0192 & 3373 & 101 & 51.7 & 200 \\
17 & P-Xylene & 106-42-3 & 0.0043 \(\pm\) 0.0011 & 1326 & 39.8 & 51.6 & 100 \\
18 & m-Xylene & 108-38-3 & 0.0031 \(\pm\) 0.0010 & 1360 & 40.8 & 51.6 & 100 \\
19 & o-Xylene & 95-47-6 & 0.0088 \(\pm\) 0.0060 & 1467 & 44.0 & 51.6 & 100 \\
20 & Syrene & 100-42-5 & 0.003 \({}^{5}\) & 156.3 & 4.70 & 23.8 & 100 \\
21 & Dimethyl disulfide & 624-92-0 & 0.0002 \({}^{5}\) & n.d. & - & 0.57 & n.d. \\
22 & Trimethylamineamine & 75-50-3 & 0.0003 \({}^{5}\) & 61 & 1.83 & 2.06 & n.d. \\
23 & Propionic acid & 79-04-9 & 0.0005 \({}^{5}\) & 386 & 11.6 & 24.4 & n.d. \\
24 & n-Butylre acid & 107-92-6 & 0.0003 \({}^{5}\) & 285 & 8.55 & 10.4 & n.d. \\
25 & i-Butylre acid & 79-31-2 & 0.0001 \({}^{5}\) & n.d. & - & 51.8 & n.d. \\
26 & Hexanoic acid & 142-62-1 & 0.0016 \(\pm\) 0.0002 & n.d. & - & 3.76 & n.d. \\
27 & Heptonic acid & 111-14-8 & 0.001 \({}^{5}\) & n.d. & - & 4.03 & n.d. \\
28 & Phenol & 108-95-2 & 0.0005 \({}^{5}\) & 166 & 4.98 & 2.11 & 5 \\
29 & m-Cresol & 108-39-4 & 0.0006 \(\pm\) 0.0002 & n.d. & - & 0.80 & n.d. \\ \hline \hline \multicolumn{7}{l}{\({}^{1}\) RD\({}_{\text{3}}\): concentration that depresses the respiratory rate by 50% due to sensory irritation; \({}^{2}\) Sensory irritation =} \\ \multicolumn{7}{l}{\({}^{0.03}\times\) RD\({}_{\text{3}}\): \({}^{3}\) DNEL: derived no-effect level for substances assumed to have a threshold exposure level; \({}^{4}\) OSHA} \\ \multicolumn{7}{l}{PEL: the permissible exposure limit (PEL) of hazardous substances according to the occupational safety and health administration (OSHA), TWA: 8 hour time-weighted average; \({}^{5}\) This value was estimated to be below the method detection limit (MDL).} \\ \end{tabular}
\end{table} 
Table 2: Concentrations of volatile organic compounds (VOCs) in vapor samples from a nicotine-free inhalator and toxic guidelines as a reference. and 1,8-cineole) were not detected in the vapor sample from the nicotine-free inhalator. It appears that some ingredients were removed during the manufacturing process. All VOCs, with the exception of acrolein, were estimated to be present at lower concentrations than the sensory irritation concentration. The increased concentration of acrolein is thought to be associated with herb processing, because when glycerol is heated, it decomposes into acrolein. Consequently, a small amount of glycerol in herbs is likely to be converted into acrolein during the manufacturing process [26].