Uncovering the Fire Risks of Expanded Polystyrene (EPS) Foam: What Underwriters May Need to Consider

Published Date: 04/06/2023
Source: Juan Dietrich - Occusurv

---

Expanded Polystyrene (EPS) is a thermoplastic foam that is widely used in industries ranging from construction to packaging. Its benefits include excellent insulation, lightweight properties, strength, durability, versatility, and shock absorbency, among other traits. Underwriters and risk surveyors often encounter EPS foam panels when visiting cold stores, warehouses, or food processing plants.

One of the most common methods of manufacturing EPS foam is by heating small polystyrene beads in the form of steam and using pentane gas as a blowing agent, which causes them to expand considerably. The beads are then moulded into a block by applying heat and pressure, which fuses them together. The block is then cut to size for its intended purpose. The finished product is a porous, low-density, and lightweight structure filled with air pockets. EPS foam is an excellent insulator because it has low thermal conductivity, meaning that heat energy is not easily conducted through air.

However, when a heat source, such as a flame, is applied, EPS foam absorbs and rapidly heats up, transferring heat across the surface area. An analogy for this is imagining you’re in a car with the windows up on a hot day. The air inside the car starts to get hot, but it takes a while for the heat to build up because the windows and metal of the car act as a barrier to keep the hot air from getting in. This is similar to how the air pockets in EPS foam act as a barrier to keep heat from getting in or out. But if you park the car in direct sunlight, the heat from the sun is much hotter than the hot air inside the car, and it can quickly make the inside of the car unbearably hot. This is similar to a flame being applied to EPS foam, which can quickly heat up and potentially catch on fire.

Foam panels typically used in cold storage or food processing industries are enclosed with a sheet metal or similar composite material, which is generally fixed to the foam with a layer of adhesives or sealant. These adhesives, like many construction materials, are designed to work within certain temperature ranges. If substantial heat is applied, the layers between the foam and sheet metal panels may start to separate, exposing the foam and allowing for fire spread.

Apart from fire load and fire spread ease, another concern for underwriters is where these panels are used for structural purposes. In those cases, history has taught us that EPS foam may lose structural stability very quickly compared to brick and mortar or reinforced steel. Additionally, firefighters face a range of other aspects when dealing with EPS fires, including flashovers, large quantities of toxic black smoke, and unknown or hidden fire spread.

Smoke ventilation is another crucial aspect that should be high on the priority list for landlords and underwriters. Often, EPS structures are found where no vertical or cross smoke ventilation has been installed. Since these panels produce thick black smoke, an engineered approach must be taken, which would or must include ventilation.

Suitable passive and active fire-fighting measures can be installed for these types of risks, but they come at a high cost. However, what about smaller sites where building size and stacking heights do not trigger a sprinkler requirement under building regulations? The risk, in my view, remains the same (generally speaking), although you may have smaller sums insured. From an underwriter’s perspective, I would argue that in the event of an uncontrolled fire without any auto-suppression and passive fire-fighting measures, the loss could be substantial, generally speaking. It is essential for underwriters to mitigate the risk as much as possible by enforcing their own insurer requirements, especially in cases where building regulations do not necessarily require additional fire safety measures.