## 2 Description of Experiments  
Figure 1 shows a schematic diagram of the 1/4 reduced-scale ISO 9705 compartment [16] and measurement equipment. Figure 1a shows a perspective view of the experimental apparatus. The frame of the compartment was made of 5 mm thick steel, and the inside was finished with a 25 mm thick blanket-type insulator. The internal volume of the compartment installed with insulation was 0.6 m(x) \(\times\) 0.9 m(y) \(\times\) 0.6 m(z). A square burner with an area of 0.02 m\({}^{2}\) was installed at the center of the compartment floor to supply fuel. Propane, through which the supply rate can be easily adjusted, was used as the fuel in the analysis of fire phenomena by stage. To uniformly supply fuel, the burner was filled with glass beads, and the fuel flow rate was controlled using a mass flow controller. The considered experimental conditions and corresponding fuel supplies are described later. Two thermocouple trees were installed at the front and rear regions of the compartment to measure the ULT. Each thermocouple tree consisted of 11 k-type thermocouples, providing temperature measurements at 0.05 m intervals in a range of z=0.05 m to 0.55 m. The bead diameter of the thermocouples is 1.0\(\pm\)0.02 mm and has a bare-bead type. Bare-bead thermocouple has an error due to radiant heat in a compartment fire environment, but it can be used to understand the thermal environment of a compartment fire [24]. Plate thermometers [25] to measure incident heat flux as well as temperature were installed on the ceiling and floor of the compartment. Inhalation probes were used to measure the chemical species concentrations of the upper layer and discharge flow. Figure 1b,c show the installation locations of the probes. The high-temperature gas sampled through the probes may cause a chemical reaction while moving to the analyzer. Taking this into account, a cooling system was used to prevent the sampled gas from showing different results from the actual values in the compartment. The triple-structured probes were cooled with an average temperature of 15 \({}^{\circ}\)C water. The water was supplied at a sufficient flow rate (4 L/min) so that the water temperature did not greatly increase even after passing through the probe inserted into the compartment. The sampled gas passed through a copper tube installed in the ice bath, and additional cooling and moisture removal were performed in this process. The cooled gas passed through a soot filter (1 \(\upmu\)m) and then flowed into a portable analyzer (MEXA-554 JK). In this study, O\({}_{2}\), CO\({}_{2}\), CO and unburned hydrocarbons (UHC) were considered for the analysis of the chemical environment. The measurement range and accuracy of the portable analyzer used to measure the concentration of chemical species are presented in Table 1.  
Figure 2 shows a schematic diagram of the various vertical opening shapes considered in this study. Incomplete combustion in the fire growth stage ended at the same time as the flame was ejected to the outside of the compartment [21]. This indicates that the start and end of this phenomenon (incomplete combustion in the fire growth stage) are closely related to the ventilation and air inflow rate through the openings. In relation to this, [PERSON] et al. [21] proposed a correlation equation on the abnormal behavior of combustion efficiency as a function of GER based on experimental results with various opening shapes. The GER is a variable to quantify the ventilation condition of compartment fires and can be obtained through Equation (1):  
\[\text{GER}\Big{(}\phi_{\text{g}}\Big{)}=\big{(}\gamma_{\text{s}}/Y_{\text{O}_{ 2}\text{a}}\big{)}\times\big{(}\,\hat{\text{m}}_{\text{f}}/\,\hat{\text{m}}_{ \text{a}}\big{)} \tag{1}\]  
where \(\gamma_{\text{s}}\) is the mass ratio of oxygen to fuel for complete combustion, and n-heptane has a value of 3.62. \(Y_{\text{O}_{2}\text{a}}\) and \(\,\hat{\text{m}}_{\text{f}}\) means the oxygen mass fraction in the air and fuel supply rate [kg/s].