Reaction to fire defines how a material behaves as a fuel when exposed to a flame or a heat source. In the industrial and passive fire protection sectors, technical textiles must meet strict regulatory requirements defined by the French M classification (NF P92-507) and the European Euroclasses (EN 13501-1). These standards measure flammability, heat release, as well as the production of toxic smoke and flaming droplets to guarantee the safety of infrastructure and operators.
The Challenges of Fire Safety and Reaction to Fire
The use of high-temperature insulating textiles is primarily involved in securing industrial processes and passive fire protection. A fabric’s classification assesses its capacity to fuel and spread a fire. It is crucial to distinguish this concept from fire resistance, which measures the duration during which a wall maintains its mechanical properties.
Each technical fabric is subjected to testing in certified laboratories, recreating real thermal exposure conditions. Whether for manufacturing insulation jackets, smoke barriers, or fire-stop seals, fire standard validation is an absolute prerequisite to ensure compliance in an industrial facility or a Public Access Building (ERP).
The M Classification: The French Combustibility Standard (NF P92-507)
The M fire classification is the historical benchmark in France, defined by the NF P92-501 to NF P92-512 series of standards. This system evaluates the combustibility of materials used in building and industry. The main test consists of exposing the sample to thermal radiation to observe its ignition time and combustion rate. The goal is to identify the extent to which the product contributes to the development of the initial fire. This classification is particularly scrutinized when integrating glass textiles or silica textiles into environments subject to welding spatters or extreme temperatures.
From M0 (non-combustible) to M4 (highly flammable)
The French standard segments materials into five strict degrees of reaction to fire, from safest to most hazardous:
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M0: Non-combustible. The material does not ignite and releases no heat.
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M1: Non-flammable. The material is combustible but does not propagate flame.
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M2: Hard to ignite. Ignition is delayed and limited.
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M3: Moderately flammable. The material burns moderately.
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M4: Highly flammable. Fire spreads rapidly. For critical industrial applications, only M0 and M1 levels are generally prescribed to guarantee an effective thermal barrier.
Gross Calorific Value (GCV) Explained
To achieve the demanding M0 level, the material must show zero ignition during the electric burner test, but above all, it must display a Gross Calorific Value (GCV) strictly lower than or equal to 2.5 MJ/kg (or 600 Kcal/kg). The GCV represents the total amount of energy released by the complete combustion of a unit of mass.
At Apronor, we design and distribute exclusive M0-classified products, such as our polyurethane-coated glass fabrics, our silicone-coated fabrics, and our caramelized glass fabrics, capable of withstanding the harshest environments without ever fueling a fire.
Euroclasses (EN 13501-1): The European Standard
To ensure the free movement of construction materials and industrial equipment within the European Union, Euroclasses were established by the EN 13501-1+A1 standard. This shared reference framework is progressively replacing national standards. It classifies products from A1 (non-combustible) to F (unclassified). This system is designed to be more comprehensive and precise than the M classification, as it incorporates real fire conditions by evaluating vital criteria for evacuation processes, such as visual toxicity and physical debris generated by the fire.
Evaluation of Smoke Opacity (Smoke – s)
Smoke toxicity and loss of visibility caused by smoke are the leading causes of death in a fire. Therefore, Euroclasses measure smoke opacity and smoke release rate, represented by the “s” (smoke) index:
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s1: Smoke release in low quantity and at a low rate (ideal for enclosed spaces).
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s2: Smoke production in medium quantity and at a medium rate.
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s3: Smoke release in high quantity and at a high rate.
Evaluation of Flaming Droplets (Droplets – d)
The second additional parameter evaluates the release of flaming particles, which are responsible for secondary fire spread, denoted as “d” (droplets):
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d0: No flaming debris is produced by the material.
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d1: Debris is generated, but its combustion lasts less than 10 seconds.
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d2: Significant production of flaming droplets or prolonged debris.
A high-security technical textile will typically display an optimal combined rating, such as A2-s1, d0, guaranteeing that it does not contribute to the fire, does not obscure emergency exits, and does not spread flames along the floor.
M Classification and Euroclasses Equivalences for Your Technical Fabrics
Transitioning from old French reports to European technical data sheets requires a clear understanding of the correspondence between both systems. Although the test methods differ, a regulatory equivalence is accepted to facilitate the specification of flame-retardant materials:
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Class M0 aligns with Euroclasses A1 or A2.
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Class M1 is equivalent to Euroclass B.
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Class M2 finds its equivalent in Euroclass C.
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Class M3 corresponds to Euroclass D.
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Class M4 is grouped under Euroclasses E and F.
The Apronor team of experts is at your service to source the certified thermal protection fabric that precisely matches your project specifications and your industry regulations.