How does Expanded Polystyrene (EPS) React to Fire?

How does Expanded Polystyrene (EPS) React to Fire?

When insulation materials are used in buildings, different aspects of fire performance such as heat release, flame spread, smoke production and toxicity must be carefully considered. Expanded polystyrene (EPS) has been extensively tested in terms of fire hazard assessments.

The behaviour and performance of a building insulation material in relation to potential fire hazards depend firstly on the chemical and nature of the material, but also on its condition at installation and its specific application.  For EPS products, note the foam density and shape, the use of bonding and additives to the surface, the location of the product relative to an ignition source, and the availability of ventilation and oxygen in the building.

Like all organic building materials, polystyrene foam is combustible and does react to fire, resulting in the decomposition of styrene and the release of carbon monoxide, smoke and water. However, the burning behaviour of EPS depends largely on end-use conditions, and whether the EPS material is with or without a fire-retardant additive. The use of flame-retardant additives (FR grade EPS) is recommended to minimise fire spreadability.

Expanded Polystyrene (EPS) manufactured by the Isowall Group is fast becoming recognized as the insulation material of choice by specifiers of “Bills of Quantities”. This comes largely as a result of our technical knowledge backed up by years of experience in the building and construction industry.

How does EPS burn?

In the first stages of a fire, there is a gradual building up of heat energy in the form of combustible gases. In case of initial fire ignition, EPS will only soften and start to melt if exposed to high temperatures above 100°C. Usually above a temperature of 200°C, the material will give off flammable gases, which then combust into flames.

Further flame sparks and ignition scenarios depend largely on the evolving fire temperature scale, duration of exposure to heat, and the oxygen availability around the product exposed to fire. Small flames are still possible with EPS already under fire unless it contains flame retardant additives that slow down spreading.

Burning will spread over the exposed surface until all material is consumed. Usually, molten EPS will not get reignited by fire sparks. For standard quality EPS, the transfer ignition temperature is high around 360°C and 370°C for FR grades. Toxic combustible gases only form above 350°C, and ignition in already melted standard grade EPS only starts at 450°C! This renders the use of EPS insulation as virtually safe and non-toxic to the environment.

It is also important to note that, unlike other insulation materials, the low density of the foam in expanded polystyrene, 98% air versus only 2% polystyrene, leads to a lower and slower release of heat during fire conditions, as there is very little burning mass.

Isowall Group manufactures and distributes the Isolite range of EPS products to users of thermal insulation, packaging, semi-rigid cushioning, and specialised shape-moulded products. Our Isolite EPS sheets are available in FR Grade.

View here more properties of our Isolite EPS range.


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