## 3 Case Studies
### Fire Safety Verification Methods--Applicable Design Scenarios
#### 3.8. Pra--Aset/Rset Analysis  
To determine the associated risk, is necessary to calculate the expected consequences, expressed in casualties. The determination of the casualties is the result of an ASET/RSET analysis and is based on a computer simulation of the fire scenarios. To reduce the burden of the simulation work, the number of simulated scenarios can be reduced by making some assumptions:  
* A smouldering fire yields no casualties as the fire is limited in size and generally its extinction is performed by occupants before the fire develops into flashover.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Tenability Criteria** & **Sole Occupant Unit** & **Corridor** & **Stairway** \\ \hline Upper Layer temperature & n & n & 150 s \\ Lower layer temperature & n & n & 90 s \\ Visibility & 240 s & 150 s & 59 s \\ FED thermal & n & n & 135 s \\ FED asphyxiant & n & n & 1011 s \\ \hline \hline \end{tabular}
\end{table}
Table 4: Results from B-Risk simulation for case #1 Blocked Exit fire.  
When suppression systems work as expected, the fire is controlled, and there are no victims.  
When the egress protection system is working as expected, untenable conditions do not arise in the corridor, hence the ASET is infinite and there are no victims (all scenarios identified with an odd number).  
The scenario where fire spreads is modelled with the following assumptions:  
The fire starts in the corridor/stairs; exit doors are not closed due to door blockade or due to failure of the self-closing mechanism. Smoke leakage through SOU doors.  
The fire starts in SOU; SOU doors remain open after the people have left the apartment (the self-closing mechanism is not working). Exit doors remain open due to door blockade or due to the failure of the self-closing mechanism.  
With these assumptions, there are 8 scenarios for each fire location, resulting in a total of 16 scenarios for each design. The fire modelling simulations are performed using the B-Risk [35] fire modelling software as used in previous studies [27; 28; 29] and requires two different scenarios for each location, one with the fire spreading into common parts and the second with fire restricted to the area of fire origin. The application of FSVM implies that the selection of fire scenarios is based on the performance requirements that have been selected in the hazard identification phase (see Chapter 8 from the FSVM Handbook [21]).  
The simulation output consists of a set of ASET values, each associated with a different scenario. The B-Risk software calculates in each time step the enclosure conditions in terms of five different tenability parameters: upper layer temperature below 200 \({}^{\circ}\)C, lower layer temperature below 60 \({}^{\circ}\)C, FED for asphyxiant gases below 0.3, FED for thermal effects below 0.3, and visibility above 10 m. The first value that triggers the above value determines the ASET, except for visibility, which is excluded in the room of fire origin and in the corridor. In these spaces, it is assumed that the occupants have familiarity with the exit route, so the visibility is not relevant. With stairs, visibility is an impeding factor as the occupants are assumed to be unfamiliar with the environment. B-Risk estimates the detection time by simulating the response time of smoke detectors or heat detectors. In one such simulation, detection time was computed as 187 s and 107 s for SOU and corridor compartments, respectively.