CEN classes
Today, all over Europe we have national standards on 'Reaction to fire'. These standards were developed some 50 years ago when building materials were mainly wood, glass, stone and cement. They were not meant for testing the big variety of building materials used in the modern world. The European Community has now developed a new set of standards that can also be used to evaluate today's building materials. The 'Reaction to fire' classes test three properties of the building material: spread of fire, smoke intensity and burning droplets.
Spread of fire
** Class A2 products must not show any sustained flaming for more than 20 seconds in the non-combustibility test. The A2 products have to be tested for Fire Contribution, smoke intensity and burning droplets.
*** Class B products flaming must not spread more than 150 mm in 60 seconds, when evaluated by a Small Flame Test. Class B products have to be tested for Fire contribution, smoke intensity and burning droplets.
There is a main distinction whether a building material can have a flashover or not. At the bottom of the page you can see what a flashover means. You can see a building with the walls still standing, but you have almost a fire explosion and the roof is 2-3 metres above the walls. Building materials in the classes A1, A2 and B cannot contribute to a flashover. Class C building materials can contribute, but after more than 10 minutes. Remember: fire fighters will normally not be at the site until 15-20 minutes after the fire has been observed.
A Class D product contributes to flashover for 2-10 minutes. A Class E product for less than two minutes. Class F is not tested.
Smoke intensity
| Class A1 | Class A2 | Class B | Class C | Class D | Class E | Class F |
| No test needed | s1: | s2: |  | s3: | Not tested | Not tested |
Smoke intensity is only tested in the classes from A2 to D. You have three intensity levels s1, s2 and s3. Smoke intensity is vital to people captured in a building on fire. Most people, dying in fires, die from smoke. And outside the building the development of smoke is equal to the amount of pollution.
Burning droplets
| Class A1 | Class A2 | Class B | Class C | Class D | Class E | Class F |
| No test needed | d0: No droplets within 600 secs | d1: Droplets burn for less than 10 secs within 600 secs | d2: Not as d0 or d1 | - or d2 | Not tested | |
Burning droplets are also only tested on building materials in the classes A2 to E inclusive. Here you have three classes: No droplets (d0), you can have droplets but they are burnt out in less than 10 seconds (d1), and droplets that burn for more than 10 seconds (d2).
