## 4 Results and Discussion  
### ASD System with One Branch Pipe with Ten Holes  
The obscuration data in the ASD system is shown in Figure 5. From case 1 to case 10, the location of the smokebox is from hole 1 to hole 10, respectively. When the smoke went through the pipe to ASD 1, the obscuration was totally different from hole 1 to hole 10. The pressure at ASD 1 for one branch pipe with ten holes in the experiment was \(-90\pm 2\) Pa. In Figure 5a, the obscuration in the smokebox is shown to be 5%/m. Obscuration was measured at ASD. Firstly, when the smokebox was located at hole 1, the obscuration at ASD 1 was around 0.95%/m, and the obscuration at ASD 1 when the smokebox located at hole 10 was 0.37%. The reason for this is that the flow rate through the hole was not equal. In this study, all holes had the same size as 5 mm, so that at the hole, which is nearest to the ASD, the pressure difference between inside and outside of the hole is largest, so the fluid that goes through that hole has the largest flow rate. This means that the flow rate of smoke from the smokebox to ASD 1 was also larger. So, the obscuration of hole 1 was the largest (0.95%/m). In addition, when the fluid moved through the pipe hole, a pressure drop also occurred. On the other hand, when the smokebox was connected with hole 10, the flow rate from the smokebox to the ASD was the smallest. Thus, the obscuration at ASD 1 was the smallest too (0.37%/m). Similarly, when the obscuration in the smokebox was changed from 5 to 10, and 15%/m, the value of obscuration was as shown in Figure 5b,c. It had the same trend as shown previously in Figure 5a. The detail obscuration at ASD when the chamber obscuration is 5, 10, 15%/m is shown in Tables 3-5. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline  & **Hole 1** & **Hole 2** & **Hole 3** & **Hole 4** & **Hole 5** & **Hole 6** & **Hole 7** & **Hole 8** & **Hole 9** & **Hole 10** \\ \hline Obscuration (\%/m) & 0.95 & 0.85 & 0.74 & 0.67 & 0.6 & 0.55 & 0.45 & 0.42 & 0.4 & 0.37 \\ \hline \end{tabular}
\end{table} 
Table 3: The obscuration at ASD 1 when chamber obscuration is 5%/m. Figure 5: The obscuration at ASD (**a**) The obscuration at ASD when chamber obscuration was 5%/m (**b**) The obscuration at ASD when chamber obscuration was 10%/m (**c**) When chamber obscuration was 15%/m. In order to predict the fire source location by using \(ASD\), the slope and obscuration ratio of \(ASD\) were investigated:  
\[Obscuration\ ratio=\frac{ASD\ Obscuration}{Chamber\ obscuration} \tag{22}\]  
The slope and obscuration ratio at \(ASD\) when the chamber obscuration is 5, 10, 15%/m is shown below in Tables 6-8. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Hole**} & \multirow{2}{*}{**Slope**} & **ASD Obscuration** & **Chamber Obscuration** & **Obscuration Ratio** \\  & & **(\%/m)** & **(\%/m)** & **(\%/m)** \\ \hline
1 & 0.10556 & 0.9533 & 5 & 0.1907 \\
2 & 0.09407 & 0.84667 & 5 & 0.1693 \\
3 & 0.08222 & 0.7400 & 5 & 0.148 \\
4 & 0.07444 & 0.66667 & 5 & 0.1334 \\
5 & 0.06 & 0.60333 & 5 & 0.1207 \\
6 & 0.0490 & 0.55 & 5 & 0.11 \\
7 & 0.03359 & 0.44667 & 5 & 0.089 \\
8 & 0.025625 & 0.42333 & 5 & 0.084 \\
9 & 0.019048 & 0.4033 & 5 & 0.081 \\
10 & 0.00982 & 0.3733 & 5 & 0.0747 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: The slope and obscuration ratio at ASD 1 when chamber obscuration is 5%/m. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & **Hole 1** & **Hole 2** & **Hole 3** & **Hole 4** & **Hole 5** & **Hole 6** & **Hole 7** & **Hole 8** & **Hole 9** & **Hole 10** \\ \hline Obscuration (\%/m) & 2.52 & 2.23 & 2.02 & 1.79 & 1.59 & 1.48 & 1.36 & 1.2 & 1.17 & 1.07 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: The obscuration at ASD 1 when chamber obscuration is 15%/m. Figure 6: The comparison of obscuration between the numerical and experimental studies (**a**) When the chamber obscuration is 5%/m (**b**) When the chamber obscuration is 10% (**c**) When chamber obscuration is 15%/m.