# High-Expansion Foam: A Risk Control Option to Increase Passenger Ship Safety during Flooding
## 3 Solutions for Damage Stability Protection Using Foam: AREST System
### Foam Characteristics
#### 3.3.4 Fire Performance  
As polyurethane foam is an organic material, it is subject to thermal decomposition when exposed directly to fire or elevated temperatures. For this reason, a range of fire tests were conducted on the foam material to assess its fire performance and identify any potential risk sources. The results of this process were then used to establish suitable RCOs, such that any risk from the foam installation in relation to fire is suitably protected against. As mentioned in previous sections, the areas targeted for foam application are enclosed void spaces, which are a category of space that pose negligible risk as a source of fire. Furthermore, introduction of foam material to the void works to displace oxygen from within the space, thus further reducing the likelihood of fire originating from any foam-protected void space. Consequently, foam installations do not pose any risk as a fire source or space of origin, but instead, the risk stems from the possibility of fire erupting in adjacent spaces. In such an event, it is possible that sufficient heat could be transferred into the foamed void, such as to give rise to foam decomposition, which could in turn result in gas overpressure within the void space. For this reason, the fire tests conducted on the foam material focused on establishing under what conditions foam thermal decomposition occurred, with specific attention given to the following parameters:  
* Temperature;
* Exposure time;
* Magnitude of decomposition;
* Gas overpressure potential. Two primary experiments were conducted in order to gain a greater understanding of the foam thermal decomposition behaviour. Within the first, differential thermal analysis (DTA) was conducted to determine the decomposition characteristics of the foam material and under which conditions this occurred. Here, loss in foam mass by virtue of thermal decomposition was measured with respect to temperature and exposure time using a thermogravimetric analyser and a sample of the foam material. The results of this analysis are summarised within Table 3 below, where it can be observed that the foam sample is relatively stable up to temperatures within the range 180-200 \({}^{\circ}\)C, beyond which more extensive decomposition occurs. Below this temperature  
Figure 10: Foam stress–strain curve under compression. range, only minor decomposition of 4% in foam mass was observed over three hours. Furthermore, limited sensitivity in the magnitude of decomposition with respect to time can be observed at temperatures below 200 \({}^{\circ}\)C, with an additional decrease in foam mass of only 3% recorded between 1 and 3 h of exposure time at 180 \({}^{\circ}\)C. It should also be noted that the results of this analysis are inherently conservative as all sides of the foam material were exposed to the temperature increments specified. However, in actuality, the degree of the foam body exposed to increased temperatures by virtue of fire would likely be localised in nature, thus leading to lower decomposition. Perhaps what is most significant about these findings is the indication that if the foamed void were equipped with suitable fire insulation, it could be ensured that decomposition temperatures were not realised. To investigate this, A-class fire insulation material from a well-known supplier was assessed in order to identify the specification that would be required to avoid foam decomposition. With the knowledge that the proposed foam technology undergoes thermal decomposition at temperatures above 160 \({}^{\circ}\)C, this can be considered the limiting temperature of the unexposed surface of the insulated bulkhead in determining the fire insulation requirements. Considering a maximum exposed surface temperature of 945 \({}^{\circ}\)C, as per IMO conditions for fire insulation testing, the results of this investigation are provided in Figure 11. Here, the temperature following 60 min at the unexposed foam/rockwood interface is plotted relative to insulation thickness.