Is polyurethane safe in case of fire?

We started a series of myths about polyurethane by talking about its behavior in the face of fire.

Polyurethane systems are present in our lives in dozens of forms. However, there are still those who question the fire behaviour of this insulating material.

Below, we offer a series of data and scientific studies that will put an end to these false myths surrounding the reaction of polyurethane systems in the event of a fire.

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What is the behaviour of polyurethane in case of fire?

The wide range of insulation products manufactured with polyurethane systems not only complies with current energy efficiency regulations, but they also meet European fire resistance standards. The polyurethane products reach between F and B-s1, d0 in the Euroclass classification.

However, in a recent study by ANPE and PU Europe which investigated the actual conditions of a fire on an insulated roof with mineral fiber (material with an A1 rating) and a polyurethane system (material with a B-s1 rating, D0).

It was the polyurethane constructive system that passed the Broof test (t2). Contrary to what Euroclass classification indicated, the mineral fiber did not prevent the spread of fire, but the polyurethane system managed to stay below the required limit, thus, (moved to start of sentence) avoiding its propagation and contributing to its extinction.

Also, in the "Fire Resistance of Wood Cladding Systems, using Polyurethane and Mineral Wool according to EN 1365-1" test, it was found that polyurethane systems are capable of responding to fire using the same materials, same fixations, the same U value (0.27) as mineral wool, but with 60% of the insulation thickness due to its lower thermal conductivity.



What is the toxicity of polyurethane fumes?

Polyurethane is a material of organic origin and therefore combustible. If it is directly affected by a fire, the fumes generated during combustion have a composition similar to that of other organic products used on a daily basis, such as wood, cork or cotton.

In addition, in order to avoid fire damage to the building structures, polyurethane systems are protected by other materials that are more resistant to fire, such as concrete, brick, plaster, mortar, etc. 

If the fire reached such proportions that this protection would give way, the polyurethane systems, when dealing with a material of organic origin, burn, but with a particularity: polyurethane does not melt or drip like other plastics (for example polystyrene), but the surface coming into contact with the flame carbonizes and protects the core, thereby maintaining some structural stability for a certain period of time.


What role does polyurethane play in the origin of a fire?

In many cases, it is heard that the origin of fires are plastic materials, like polyurethane, that are used in the isolation of the building, but this is certainly not true.

Polyurethane has the peculiarity that when it comes into contact with the flame, instead of melting, it carbonizes, protecting the core of the fire. This causes the structure to remain stable for some time.

For this reason, polyurethane systems are never the origin of a fire. The beginning must be a different one and the isolation, if achieved, will be based on the design of the structural element in which it is integrated, and the time that elapses as the fire develops. The design of the building is key when it comes to fire safety.

It is important to consider that most of the fires are not caused by the materials used in the insulation of the industrial units or houses, but by a poor management of the waste accumulated in them or by the human factor.

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Safety against the fire response of polyurethane

Construction solutions that integrate polyurethane insulation products contribute to the fire safety of the building and its occupants. False myths such as their toxicity or that they are easily inflammable have been denied by the different tests that have been carried out to verify this resistance.

In addition, the fire safety of polyurethane has been tested at various junctures in the building industry.

Polyurethane products have performed very similarly to other materials classified in higher Euroclasses in the interior insulation of façades with insulation systems using laminated plasterboard, in the insulation of façades with SATE exterior insulation or in the insulation of roofs under waterproofing bituminous membranes.

Specifically, when comparing the reaction of polyurethane (PU) plates and mineral wool (MW) plates, no differences were found in fire response, so it can be stated that the use of polyurethane systems for the insulation of the building is safe and efficient, also in relation to fire response.


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