EN 13501-1 standard for fire classification of construction materials: Overview of performance classes & criteria

In Europe, the fire safety of construction products and materials is generally assessed using the EN 13501-1 classification standard, which categorizes building products and specifies the tests required to evaluate their reaction-to-fire characteristics. The test results are then used to classify construction products into fire performance classes, which largely determine the types of environments they can be used in.

The legal framework for fire classification in the EU is the Construction Products Regulation (CPR), which requires manufacturers to provide a declaration of performance and affix the CE marking to most construction products before bringing them to market. To be eligible for the CE marking, the product must meet the specifications outlined in the applicable harmonized standard in terms of its essential characteristics, including fire safety.¹

Beyond EU-wide requirements, companies must also consider the national regulations of member states where construction products are used. The specific fire classification required for a given product in a given application ultimately depends on these national building regulations.

This article provides an overview of the fire classes outlined in EN 13501-1 and the criteria for obtaining each classification. If you have further questions about the topic or are interested in purchasing the tests, do not hesitate to contact us.

Categorization of construction products under EN 13501-1

The EN 13501-1 standard divides construction products into three categories based on their physical characteristics:²

• Construction products excluding floorings. These can be classified into fire performance classes A1, A2, B, C, D, E, and F.

• Floorings, for which the corresponding classes are A1fl, A2fl, Bfl, Cfl, Dfl, Efl, and Ffl.

• Linear pipe thermal insulation products, which can be classified as A1L, A2L, BL, CL, DL, EL, and FL.

Fire performance classes and classification requirements

Reaction to fire performance evaluation by EN 13501-1 involves assessing several parameters, including ignitability, flame spread, and total heat release. The performance criteria for achieving specific fire ratings are outlined below.

Performance criteria for classes A1, A1fl, and A1L

Building products that fulfill the requirements for classes A1, A1fl, and A1L are considered non-combustible, meaning that they do not contribute to the spread of fire. Such materials are ideal for use in applications that require a high degree of fire resistance, such as high-rise buildings, schools, hospitals, and care facilities.

According to EN 13501-1, achieving the highest fire safety rating requires that the following criteria are met, regardless of the type of construction product:

• Non-combustibility test (EN ISO 1182): temperature rise ≤ 30 °C, mass loss ≤ 50 %, no sustained flaming, AND

• Gross heat of combustion test (EN ISO 1716): gross calorific potential under 2,0 MJkg⁻¹ for homogenous products and substantial components of non-homogenous products.

Certain materials known to have a low level of combustibility can be classified as A1 without testing. These include mineral wool, cement, glass, ceramics, and products thereof with < 1% organic material content.³

Performance criteria for classes A2, A2fl, and A2L

While class A2, A2fl, and A2L construction products are not fully non-combustible like class A1 products, they have very limited combustibility and do not accelerate the spread of fire. One of the following tests with the following results is required to obtain the second-highest fire rating for all construction product categories:

• Non-combustibility test (EN ISO 1182): temperature rise ≤ 50 °C, mass loss ≤ 50 %, duration of flaming ≤ 20 s, OR

• Gross heat of combustion test (EN ISO 1716): gross calorific potential ≤ 3,0 MJkg⁻¹ for homogenous products and substantial components of non-homogenous products.

In addition, products excluding flooring and linear pipes must meet the following criteria for A2 classification:

• Single burning item test (EN 13823): fire growth rate ≤ 120 Ws⁻¹, lateral flame spread < edge of specimen, total heat release in 600 seconds  ≤ 7,5 MJ

The single burning item test is also required to classify linear pipes as A2L. The necessary results are otherwise the same, but the fire growth rate can be higher (≤ 270 Ws⁻¹).

For flooring to be classified as A2fl, the following test is required instead:

• Reaction to fire test for flooring (EN ISO 9239-1): critical flux ≥ 8,0 kWm⁻²

Performance criteria for classes B, Bfl, and BL

Class B construction products are considered combustible but have a very limited contribution to fire. For products other than flooring, this is confirmed through the following tests:

• Single burning item test (EN 13823): fire growth rate ≤ 120 Ws⁻¹ (or ≤ 270 Ws⁻¹ for class BL linear pipes), lateral flame spread < edge of specimen, total heat release in 600 seconds ≤ 7,5 MJ, AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 60 seconds, following a 30-second exposure.

The requirements for flooring to receive a Bfl classification are the following:

• Reaction to fire test for flooring (EN ISO 9239-1): critical flux ≥ 8,0 kWm⁻², AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 20 seconds, following a 15-second exposure

Performance criteria for classes C, Cfl, and CL

Class C construction products have a limited contribution to fire, as demonstrated by the following test results:

• Single burning item test (EN 13823): fire growth rate ≤ 250 Ws⁻¹ (or ≤ 460 Ws⁻¹ for class CL linear pipes), lateral flame spread < edge of specimen, total heat release in 600 seconds ≤ 15 MJ, AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 60 seconds, following a 30-second exposure.

For class Cfl flooring, the following results are required instead:

• Reaction to fire test for flooring (EN ISO 9239-1): critical flux ≥ 4,5 kWm⁻², AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 20 seconds, following a 15-second exposure

Performance criteria for classes D, Dfl, and DL

Class D construction materials have a medium contribution to fire. This is confirmed through the following test results for products other than flooring:

• Single burning item test (EN 13823): fire growth rate ≤ 750 Ws⁻¹ (or ≤ 2,100 Ws⁻¹ for class DL linear pipes). Linear pipes must also have a total heat release of ≤ 100 MJ in 600 seconds. AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 60 seconds, following a 30-second exposure.

For flooring, classification as Dfl is achieved with the following test results:

• Reaction to fire test for flooring (EN ISO 9239-1): critical flux ≥ 3 kWm⁻², AND

• Ignitability with a small flame (EN ISO 11925-2): flame spread ≤ 150 mm within 20 seconds, following a 15-second exposure

Performance criteria for classes E, Efl, and EL

Class E materials have a limited degree of fire resistance, as demonstrated by the following result from the EN ISO 11925-2 ignitability test:

• Flame spread ≤ 150 mm within 20 seconds, following a 15-second exposure. This requirement applies to all construction product categories (flooring, linear pipes, and other products).

Class F, Ffl, and FL construction products

Materials that do not fulfill the criteria for Class E in terms of their reaction-to-fire characteristics are placed into Class F. Such materials are considered easily flammable and unsuitable for use in environments where fire resistance is required.

Classification for smoke production and flaming particles

In addition to the main fire classification, EN 13501-1 requires construction products in classes A2, B, C, and D to be evaluated in terms of their tendency to produce smoke and flaming particles. Class E products are also given an additional classification for flaming particles in certain cases.

Smoke production

Construction products other than flooring and linear pipes are classified into the following smoke production classes, based on data from the single burning item test (EN 13823):

• s1: smoke growth rate ≤ 30 m²s⁻² and total smoke production in 600 seconds ≤ 50 m²

• s2: smoke growth rate ≤ 180 m²s⁻² and total smoke production in 600 seconds ≤ 200 m²

• s3: the conditions for s1 or s2 are not met

For linear pipes, the required test results for placement in different smoke production classes are the following:

• s1: smoke growth rate ≤ 105 m²s⁻² and total smoke production in 600 seconds ≤ 250 m²

• s2: smoke growth rate ≤ 580 m²s⁻² and total smoke production in 600 seconds ≤ 1,600 m²

• s3: the conditions for s1 or s2 are not met

The smoke production classification of flooring is based on results from the EN ISO 9239-1 reaction to fire test:

• s1: smoke ≤ 750 % x minutes

• s2: the condition for s1 is not met

Flaming droplets

The assessment of flaming droplets or particles is not applicable to flooring. For other construction products, including linear pipes, classification is based on the results of the EN 13823 test:

• d0: no flaming particles are formed within 600 seconds

• d1: no flaming particles persisting longer than 10 seconds are formed within 600 seconds

• d2: the conditions for d0 or d1 are not met

A d2 rating is also given if the paper used in the EN ISO 11925-2 test is ignited. Class E construction products can only be given a d2 rating; if the paper is not ignited during the EN ISO 11925-2 test, no flaming droplet classification is given.

All EN 13501-1 fire classification tests in one place

Measurlabs provides fire testing and classification services according to EN 13501-1 for various types of construction materials. You can contact our experts through the form below for more information and a quote. Please describe the product in detail and tell us which fire performance class you are aiming for to help us prepare the offer faster.