Is Extruded Polystyrene Flammable? 

This article will answer the question, “is extruded polystyrene flammable?” It also covers several topics about extruded polystyrene, its properties, and how to respond to fire ignition caused by extruded polystyrene.

Is Extruded Polystyrene Flammable?

Yes, extruded polystyrene is flammable. It is essential to keep polystyrene properly in any assembly because it is highly combustible. 

However, in actual use, the burning characteristics of the substance are influenced by environmental factors and the substance’s inherent features. Expanded polystyrene products are not a fire threat when fitted correctly.

What Is Extruded Polystyrene?

Extruded polystyrene or XPS is a rigid thermoplastic material produced from polystyrene (PS) plastic, a hydrocarbon polymer obtained from two petroleum products, benzene and ethylene.

The manufacturing process for extruded polystyrene (XPS) products is generally similar to that for expanded polystyrene (EPS) products. Both also have the same primary material, namely PS. 

In the manufacturing process, polystyrene crystals are combined with various unique additives and blowing agents. 

The multiple components were loaded onto the extruders. There, the elements of the mixture combine precisely as they should, and the melting process takes place under carefully regulated circumstances such as high temperature and pressure. 

This results in producing a hot and dense liquid plastic with a thick consistency. The liquid should then be passed through the dice. 

As it passes through the dice, it undergoes expansion, which results in foam formation. The material must be shaped, allowed to cool, and then cut into the appropriate form.

In general, extruded polystyrene is more expensive than expanded polystyrene (EPS) because it has a closed cell structure, which makes it typically more durable. 

It also has a higher mechanical performance. Its density is between between 28 and 45 kg/m3, approximately. 

Since EPS and XPS both start with the same raw ingredients, crude oil serves as the fundamental component of each of these products. 

The manufacturing process for expanded polystyrene and extruded polystyrene are just somewhat distinct from one another.

In the same way as EPS does, XPS can be used for a wide range of different things. The insulation of buildings, roofs, and even concrete floors can be accomplished with its support. 

Crafts and model making can also benefit from the versatility of extruded polystyrene material, particularly for the creation of architectural models.

Expanded and extruded polystyrene both have a closed-cell structure, but they allow water molecules to pass through, so neither type can be considered a vapor barrier.

What Are the Properties of Extruded Polystyrene?

Compressive Strength

XPS plastic has excellent compressive strength. Typically, XPS plastic boards have compression strengths of 100 psi or more.

Thermal Characteristics

R-value is a unit used to assess a material in conducting heat. The higher the R-value, the more resistant the material is to heat conduction, making it suitable for use as an insulation material.

XPS plastic has an even closed-cell distribution structure. This makes XPS plastic has a reasonably significant R-value, namely R-5/25 mm. This figure shows that XPS plastic is twice as resistant to heat as other insulation materials of the same thickness.


When used as insulation for houses or other buildings, XPS can reduce the energy consumption needed to regulate the room temperature because it has good thermal conductivity properties.


Because it is a thermoplastic material, XPS will not rot. This plastic is also resistant to microorganisms found in the soil. Typically, XPS boards can last up to 50 years.

In addition, XPS, a thermoplastic, can be re-melted and recycled into new XPS products.

How To Respond In The Event Of A Fire Caused By Extruded Polystyrene?

There is a potential for a fire to develop due to the presence of extruded polystyrene. In the case that there is a fire, the following procedures need to be carried out:

  • In the event of a fire or explosion, there is a possibility that you will be exposed to the deadly gas. It is highly recommended that you protect yourself by wearing a mask that filters the air you breathe.
  • To keep the containers from catching fire, it is recommended that water be sprayed into them. Water is your best bet if you want to put out a fire that’s been started in a hot container. To extinguish the flames, this method must be carried out multiple times.
  • Spraying water directly onto the flames won’t do anything but make the situation worse. There is a possibility that the fire will emit sulfuric fumes, which have an unpleasant odor and are potentially hazardous to anyone who breathes them in. Be conscious of it!
  • At all times, firefighters are expected to wear specific gear, including a coat resistant to flames, gloves, a helmet with face protection, and boots made of rubber.

You can learn more here.


There is a risk of fire ignition when working with extruded polystyrene. As a result, it must be handled with caution and under all applicable health and safety standards.

Frequently Asked Question (FAQs): Is Extruded Polystyrene Flammable?

What temperature does styrofoam reach before it starts to ignite?

When exposed to a naked flame or spark at a temperature of approximately 680 degrees Fahrenheit, polystyrene, the chemical name for Styrofoam, can quickly catch fire (360 Celsius). It will auto-ignite about 800 degrees Fahrenheit (427 Celsius).

Is there a risk of fire when using foam board?

According to a technical bulletin published by the OSHA in 1989, “Rigid polyurethane and polyisocyanurate foams will, when lit, burn fast and produce tremendous heat, dense smoke, and fumes that are unpleasant, combustible and poisonous.”

What are some of the applications for insulation made of extruded polystyrene?

Extruded Polystyrene Board is an excellent choice for various applications, including but not limited to wall and ceiling insulation, cool rooms and refrigeration, under the concrete slab, and even architectural modeling or the creation of hobby models. 

For residential and commercial applications alike, extruded polystyrene proves to be the superior insulating material.


What was missing from this post which could have made it better?

Leave a Comment