Purenit & flammability - important information

1.12.2025 Ivan Landa

When fire is mentioned in connection with building materials, most people become alarmed. It is logical, each of us wants to be sure that his house or building is strong and durable, but also safe in case of possible contact with flames. Nowadays, a number of new materials appear on the market, and one of them is purenit. And the question of its flammability is one of those that people often ask. Does it burn? Is it safe? And why is it so widely used in modern construction?

You will get the answer to these questions in this article, because in the following lines we will look at what purenit actually is, what its technical properties are, how it reacts to fire and how it compares to other materials. Thanks to this, you will get a clear picture and find out if purenit is a suitable choice for your project

What is purenit?

Purenit is a modern functional building material made of rigid polyurethane foam (PUR/PIR) and is made from recycled polyurethane residues and scraps. It is light, but at the same time very strong - its bulk density is around 550 kg/m³ and its compressive strength reaches a minimum of 7.1 MPa.

In addition, there are a number of other advantages: purenit is resistant to moisture, does not rot or mold, is stable even under long-term loads and easily withstands a wide range of chemicals, including mineral oils and solvents. Another great advantage is its low thermal conductivity, thanks to which it works as a good insulator.

It is precisely because of its properties that purenit is used where other materials fail, for example in bathrooms, on facades, in structures exposed to moisture, as door filling, in window sills or even as a base under window frames. Simply put, wherever strength, durability and insulating capabilities need to be combined.

Is purenit flammable?

The question that interests everyone: how does purenit behave in contact with fire?

Reaction to fire class

According to the European standard EN 13501-1, Purenit is classified as class E, which means that it is normally flammable. However, this does not mean that it is dangerous. In practice, this means that it can burn, but after the removal of direct flame, it usually stops burning spontaneously.

For buildings where even greater emphasis is placed on fire safety, there is also a purenit C variant. This type contains added flame retardants and achieves a higher rating - class C. This is a level that corresponds to materials with significantly better resistance to flames.

How it behaves when burning

A big plus is that purenit does not smolder, does not melt and does not drip when burning. This minimizes the risk that burning drops could ignite other materials in the vicinity. Burning drops that drip from some plastics are very dangerous because they can cause the fire to spread to places where there was no flame originally. Purenit does not suffer from this risk.

How does it compare to other materials?

In order to assess what class E or C means in practice, we looked at other commonly used building materials:

• Wood - a traditional and popular material, but it behaves worse in a fire than purenit. Wood burns for a long time and can continue to glow even after the flame is removed.
• PVC - PVC-type plastics melt and drip when burning, which is very dangerous. In addition, they can release unpleasant and harmful substances.
• Concrete - is a non-combustible material, but its thermal insulation properties are very limited and its mechanical resistance to moisture is not comparable to purenit.
• Polystyrene - is known for its flammability. In direct fire, it melts quickly, drips and the fire spreads very quickly over it.

From the comparison, it is clear that purenit stands somewhere between traditionally non-combustible materials, such as concrete or mineral insulation, and common plastics or polystyrene. Thanks to its stability and safe behavior in contact with fire, it provides higher safety than many other commonly used materials.