## 2 Experimental Method and Conditions
### Calculation of CO and Soot Yields  
As shown in Figure 1, the CO yield was calculated using the cross-sectional mean temperature (\(T_{d}\)), flow rate (\(V_{d}\)), volume fraction of CO (\(X_{CO}\)) measured within the exhaust duct, and MLR measured with a load cell. The CO yield (\(y_{co}\)) is expressed as the ratio of the time-averaged mass flow rate (\(\overline{m_{co}}\)) of CO to MLR (\(\overline{m_{f}}\)), as shown in Equation (1).  
\[y_{co}=\overline{m_{co}}/\overline{m_{f}} \tag{1}\]  
As mentioned in the introduction, selecting start and end points in the time averaging process of the measurement data can have a significant effect on quantitative changes in physical quantities. In particular, in studies involving cone calorimeters, various criteria have been applied to define \(\overline{m_{f}}\) during the entire burning time [16; 38; 45]. In this study, \(\overline{m_{f}}\) was calculated as the mass variation (\(m_{90}-m_{10}\)) of the section corresponding to between 10% (\(t_{10}\)) and 90% (\(t_{90}\)) of the entire mass loss using Equation (2); \(\overline{m_{co}}\) was calculated using Equation (3) [38].  
\[\overline{m_{f}}=(m_{90}-m_{10})/(t_{90}-t_{10}) \tag{2}\]  
\[\overline{m_{co}}=\int\limits_{t_{10}}^{t_{90}}Y_{co}(t)\dot{m_{e}}(t)dt/(t_{9 0}-t_{10}) \tag{3}\]  
where \(Y_{co}\) is the mass fraction of CO, which was converted using the equation \(Y_{CO}=X_{co}MW_{co}/MW_{air}\). \(m_{e}\) indicates the mass flow rate within the exhaust duct, which was calculated using the equation \(\dot{m_{e}}\)=\(\rho_{e}A_{D}V_{D}\). Moreover, \(MW\), \(A_{D}\), and \(V_{D}\) indicate the  
Figure 2: Photographs of a cone heater and the schematics of exhaust hood heights considered.  
molecular weight, area of the exhaust duct, and average velocity within the exhaust duct, respectively. The density inside the exhaust duct (\(\rho_{e}\)) is calculated as the mean temperature measured at three different locations in the radial direction. For most fire calculations, the average molecular weight of exhaust gases is similar to that of air, and it was assumed that the value is primarily determined by temperature [29]. Specifically, \(\rho\) (\(kg/m^{3}\)) is calculated based on \(352.8/T\)(K).  
Regarding the calculation of the soot yield (\(y_{soot}\)), the light extinction coefficient has the relationship of optical path distance (\(L\)) and permeation rate based on Bouguer's law, as shown in Equation (4) [46].  
\[k(t)=-ln(I(t)/I_{0})/L \tag{4}\]  
Here, \(I_{0}\) and \(I\) represent the voltage of a photo transistor before and after ignition, respectively. The mass concentration of the smoke (\(m_{soot}\)) can be calculated using Equation (5). \(k_{m}\) is the mass specific extinction coefficient, which is dependent on the fuel in which hydrocarbon fuels have a coefficient of 8.4, while wood materials have a coefficient of 7.6 [29]. Then, the mass flow rate of the smoke (\(m_{soot}\)) is expressed as the product of the volume flow rate (\(\dot{V}_{e}\)) within the exhaust duct, as shown in Equation (6). Finally, \(y_{soot}\) was calculated using Equation (7).  
\[m_{soot}(t)=k(t)/k_{m} \tag{5}\]  
\[\dot{m}_{soot}(t)=m_{soot}(t)\dot{V}_{e}(t) \tag{6}\]  
\[y_{soot}=\overline{m}_{soot}/\overline{m}_{f}=\left|\int\limits_{\mathbf{I}_{ 10}}^{t_{90}}\dot{m}_{soot}(t)dt/(t_{90}-t_{10})\right|/\overline{m}_{f} \tag{7}\]