# Fire Risk Analysis in Large Multi-Compartment Structures Using a Hybrid Multiscale Approach
## 3 Proof of Concept
### Application to a Multi-Story Office Building
#### 3.1.1 Zone Model Results  
As mentioned earlier, the zone model was beforehand used to simulate the development of a fire in each compartment [14]. Table 2 gives the thermal properties of the materials making up the walls and partitions of the building. Given the geometry, fuel load, and ventilation conditions, eight separate compartment fire scenarios were investigated (Table 3). Table 3 presents the results obtained with the zone model, in terms of times of flashover, decay, and extinguishment. For all simulations, the time step was 50 \(\upmu\)s. A run for the simulation of 1 h of fire takes less than 2 CPU minutes on a PC with Intel(r) Core i7-4770 (3.40 GHz) and 16 GB RAM. The first two fire scenarios correspond to a private office with a window that can be initially closed or opened (due to glass breakage by external flames) when the fire starts \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Material** & **Conductivity** & **Density** & **Specific Heat** & **Emissivity** \\  & **(W/m/deg.)** & **(kg/m3)** & **(J/kg/deg.)** & **Emissivity** \\ \hline \hline \multicolumn{1}{c}{Plasterboard BA13} & 0.25 & 900 & 1000 & 0.9 \\ \multicolumn{1}{c}{Rock wool} & 0.038 & 60 & 1030 & 0.9 \\ \multicolumn{1}{c}{Concrete} & 1.75 & 2300 & 2160 & 0.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Thermal properties of the constituent materials of the walls and partitions of the four-story building (manufacturer’s data). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Fire** & **Type of** & **Windows** & & **Time (mm/s/s/\({}^{\prime\prime}\))** & \\
**Scenario** & **Compartment** & **Open Doors** & **Open 1/Closed** & **Flashover** & **Decay** & **Extinguishment** \\ \hline \hline \multirow{2}{*}{\begin{tabular}{c} FS1 \\ FS2 \\ \end{tabular} } & Private & 1 (e.g., A01) & 0/1 & 7\({}^{\prime}\)49\({}^{\prime\prime}\) & 9\({}^{\prime}\)20\({}^{\prime\prime}\) & 29\({}^{\prime}\)00\({}^{\prime\prime}\) \\ \hline \multirow{2}{*}{\begin{tabular}{c} FS3 \\ \end{tabular} } & & 4 (e.g., A07 with & & \\  & & emergency exits closed) & - & 9\({}^{\prime}\)20\({}^{\prime\prime}\) & \\ \hline \multirow{2}{*}{\begin{tabular}{c} FS4 \\ \end{tabular} } & & 0/1 & 9\({}^{\prime}\)20\({}^{\prime\prime}\) & & \\ \cline{2-5}  & Co-working & 4 (e.g., A09 with stairwell) & 1/0 & NF & \\ \cline{2-5}  & compartment & 5 (e.g., A07 with & & \\  & & emergency exits open) & - & NF & \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} FS7 \\ \end{tabular} } & & 6 (e.g., B08) & - & NF & \\ \hline \hline \multirow{2}{*}{
\begin{tabular}{c} FS8 \\ \end{tabular} } & & 3 (A08) & - & 18\({}^{\prime}\)46\({}^{\prime\prime}\) & 19\({}^{\prime}\)40\({}^{\prime\prime}\) & 30\({}^{\prime}\)10\({}^{\prime\prime}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Zone model results for the eight fire scenarios. NF means no flashover. Figure 9: HRR time curves for the three types of building compartments. in the compartment. As expected, ventilation conditions influence the onset of flashover. When the window is initially open (FS2), the burning compartment does not reach the flashover, due to energy losses through this opening. In the opposite case (FS1), flashover occurs after \(7^{\prime}49^{\prime\prime}\) of fire. The same result is found when comparing the simulation results for fire scenarios in co-working spaces. When the compartment has no window (FS3) or when it is initially closed (FS4), the fire is fully developed after \(9^{\prime}20^{\prime\prime}\). When the window is initially open (FS5) or when the compartment has six doors open (FS7), flashover does not occur. Again, smoke evacuation through the openings generates heat losses that limit the temperature rise of the gas in the hot gas layer.