## 3 Results and Discussion
### Primary Processing Scattering Light Distribution According to Smoke Particle Color
As shown in the figure, at the time of detector activation, the OD of white smoke generated from filter paper was 0.104 m\({}^{-1}\), that of black smoke from kerosene was 0.203 m\({}^{-1}\), and that of PU from gray-black smoke was 0.139 m\({}^{-1}\). As these values represent the OD at the moment the detector was activated in repeated experiments, the results confirm that OD is closely related to the smoke particle color and the SSA. In other words, the white smoke generated from filter paper activates the detector at a relatively low OD value compared with those for kerosene and PU. Thus, the detector activation OD values, according to combustible, as presented in the figure, were applied directly to the calculation of the analysis criteria. Specifically, these dimensionless values were used for the OD of each, and generated and measured according to the combustible. Figure 7 shows the rate of change of the measured values from the initial values for the optical properties of each combustible by applying the analysis criteria presented in Table 1. Here, the x-axis (OD/OD\({}_{\text{detector activation}}\)) is dimensionless, representing the moment activated OD was applied to all ODs measured in real time through repeated  
Figure 6: Detection of optical density through a smoke detector for each combustible. experiments. Therefore, \(x=1\) represents the activation moment of the photoelectric smoke detector, \(x<1\) is the time before, and \(x>1\) is the time after. Figure 7a (criterion I) shows the ratio of the forward and backward scattering ratios to the 0\({}^{\circ}\) light extinction signal. For all the data plotted, the slope of the linear fit for filter paper is 0.2095, that for kerosene is 0.1261, and that for PU is 0.3091. Figure 7b shows the ratio of forward scattering to backward scattering by applying criterion II. The results confirm that filter paper has a value of 0.1755, kerosene a value of 0.0707, and PU a value of 0.2172. Finally, Figure 7c shows the ratio of light scattered to light extinction, to which criterion III is applied; the value for filter paper is 0.2109, that for kerosene is 0.1730, and that for PU is 0.2775. As described above, the slope for each type of combustible can be derived for the sections where data are plotted, and it can be confirmed that it is difficult to see a clear trend between combustibles. Therefore, as the plotted data are the result of minute voltages measured inside the LSC, it is necessary to clearly distinguish the relationship between the optical properties of the smoke particles generated from each combustible. Thus, it is reasonable to apply the data re-established through the zero resets of the initial value of the rate of change. Figure 7: Comparison of results for the distribution of optical analysis criteria for the primary ratio according to the scattering angles (\(I=150^{\circ}\)). Figure 8 shows the light scattering characteristics according to smoke particle color. The x-axis is dimensionless, representing the moment activation OD was applied to all OD values, measured in real time through repeated experiments. Therefore, \(x=1\) represents the moment of detector activation. The y-axis shows the ratio of the light-scattering signal, measured at all 11 detection angles installed inside the LSC, to the light extinction signal, measured at 0\({}^{\circ}\) (The detection angles of 15\({}^{\circ}\) to 165\({}^{\circ}\) for the scattering angle are represented via the values of index \(j\), from 1 to 11). The results confirm that there is a distribution range for each combustible, excluding the initial smoke concentration when the combustible begins to burn. Specifically, filter paper exhibits a very wide distribution, with values ranging from 10 to 40, because light scattering is dominant for its smoke particles relative to those of the other combustibles. As a result, for kerosene and PU, corresponding to black and gray-black smoke, respectively, the ratio of the light scattering for all angles to the light extinction is relatively small.