## 2 The Model
### Fire Scenarios  
The ten tests performed correspond to various combinations and loads of the fuels presented above, as well as two levels of containment of the device, depending on whether the bulkhead door was closed or open (Table 3). For all tests, the exhaust volumetric flow rate at the ceiling of compartment 1 was initially set to 800 m\({}^{3}\)/h. There was no other mechanical ventilation. The openings on the WEST wall of compartment 1 were kept open, as well as the natural opening at the bottom of the bulkhead door when this door was closed. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multirow{2}{*}{**Fuel**} & **Chemical** & **Density** & **Yields of Fire Products (g/g)** & \(\Delta h_{ch}\) & \multirow{2}{*}{\(\chi_{r}\)} \\  & **Formula** & **(kg/m3)** & **Soot** & **CO** & **HCN** & **(MJ/kg)** & \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Heptane \\ PMMA \\ Dry untreated fir 1 \\ PU foam 2 \\ \end{tabular} } & C\({}_{2}\)H\({}_{16}\) & 680 & 0.037 & 0.010 & 0 & 41.2 & 0.305 \\  & C\({}_{5}\)O\({}_{2}\)H\({}_{8}\) & 1160 & 0.022 & 0.010 & 0 & 24.2 & 0.302 \\  & C\({}_{6}\)O\({}_{10.2}\)H\({}_{4.98}\) & 420 & 0.015 & 0.004 & 0 & 12.4 & 0.207 \\  & C\({}_{6.3}\)O\({}_{7.1}\)H\({}_{2.1}\)N & 30 & 0.227 & 0.031 & 0 & 28.0 & 0.520 \\ \hline \end{tabular}  
* assimilated to wood pine [21]. 2 The PU foam selected is a flexible, water-blown foam composed of two-thirds TDI (toluene discoyanate) and one-third polyol. It does not contain a flame retardant. This type of foam is used for the filling of mattresses, seats of chairs, armchairs, or benches. It is here assimilated to GM23 flexible PU foam [21].  
\end{table} 
Table 2: Fuel properties [21]. Figure 7: Schematics showing the locations of some thermocouples in compartment 1 to measure (**a**) gas and (**b**) wall temperatures. The fire source was a combination of two of the following unit fuel fire sources (Figure 8):  
* A 70 cm diameter pan filled with heptane;
* A wooden crib, formed by stacking 10 crisscrossed layers of 6 DUF sticks. Each stick was 0.5 m long, with a 3 cm square section. A holding grid was used to prevent the glowing sticks from falling out of the 70 cm diameter pan due to the collapse of the crib;
* Two PUF blocks, stacked in a 70 cm diameter pan. Each block has dimensions of 0.62 m \(\times\) 0.62 m \(\times\) 0.1 m;
* Four sheets of PMMA, arranged horizontally in a 70 cm diameter pan. Each sheet has dimensions of 0.2 m \(\times\) 0.5 m \(\times\) 0.03 m.  
For the tests using dry untreated fir and PMMA as fuel, the combustible elements were arranged in such a way that the flame generated by their combustion clings to the edge of the pan and occupies its entire surface, which makes it possible to assimilate the effective area of the fire source to that of the pan (0.385 m\({}^{2}\)). Therefore, in any test, the total area of the multi-fuel fire source was 0.77 m\({}^{2}\). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Test** & **Fuel(s)** & **Bulkhead Door** \\ \hline
1 & DUF (8.46 kg)/PUF (2.3 kg) & \\
2 & PMMA (7.37 kg)/PUF (2.33 kg) & \\
3 & Heptane (5.34 kg)/PMMA (7.39 kg) & Closed \\
4 & Heptane (5.37 kg)/PUF (2.33 kg) & \\
5 & DUF (8.49 kg)/PMMA (7.41 kg) & \\ \hline
6 & DUF (8.49 kg)/PUF (2.33 kg) & \\
7 & PMMA (7.41 kg)/PUF (2.32 kg) & \\
8 & Heptane (5.33 kg)/PMMA (7.39 kg) & Open \\
9 & Heptane (5.37 kg)/PUF (2.29 kg) & \\
10 & DUF (8.5 kg)/PMMA (7.4 kg) & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Fire scenarios. Figure 8: Fire sources involving (**a**) DUF and PUF (tests 1 and 6), (**b**) PMMA and PUF (tests 2 and 7), (**c**) heptane and PMMA (tests 3 and 8), (**d**) heptane and PUF (4 and 9), and (**e**) DUF and PMMA (tests 5 and 10). As shown in Figure 5, the first fuel pan was placed in the center of compartment 1, while the second one was moved to the WEST wall, with its center 50 cm from the wall. Ignition of heptane and PUF was achieved by exposing the fuel to the flame of a gas burner for a few seconds.