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2026-11-03T09:18:26

Reaction-to-Fire Classes A1, A2, B-s1,d0: What Euroclass EN 13501-1 Means

建材防火等级A1、A2、B-s1,d0：欧洲EN 13501-1分级含义与选材

A reaction to fire class in the Euroclass system of EN 13501-1 shows how much a material contributes to a fire, not how long a wall resists it. A1 is non-combustible, then A2, B, C, D, E and F are increasingly combustible. Extra codes s1–s3 rate smoke and d0–d2 rate flaming droplets, so B-s1,d0 means limited combustibility, low smoke and no flaming droplets. These codes often appear on brochures for imported boards, panels and insulation.

Key Facts

Reaction to fire, not fire resistance

EN 13501-1 assesses reaction to fire: whether a material ignites easily, how fast flame spreads and how much heat it releases. This differs from fire resistance (for example a 60-minute wall), which is covered by other parts of the EN 13501 series. In the EU these classes appear in the declaration of performance and CE marking; the class required for each use is set by national building rules.

The standard has three product groups: general products (A1–F), floorings with the suffix "fl" (A1fl–Ffl), and linear pipe insulation with the suffix "L".

What each main class means

  • A1: non-combustible, no contribution to fire.
  • A2: very limited combustibility; EN ISO 1182 (rise ≤ 50 °C, flaming ≤ 20 s) or calorific value ≤ 3.0 MJ/kg, plus the SBI test.
  • B: combustible but very limited contribution; passes SBI and the EN ISO 11925-2 small-flame test (spread ≤ 150 mm within 60 s).
  • C: limited contribution; fire growth rate ≤ 250 W/s and total heat ≤ 15 MJ.
  • D: medium contribution; growth rate ≤ 750 W/s.
  • E: passes only the small-flame test (spread ≤ 150 mm within 20 s).
  • F: fails class E or not tested; considered easily flammable.

Smoke (s) and droplet (d) codes

Classes A2, B, C and D must carry smoke and droplet codes:

  • s1: smoke growth ≤ 30 m²/s² and total ≤ 50 m² in 600 s; s2: ≤ 180 m²/s² and ≤ 200 m²; s3: fails s1/s2.
  • d0: no flaming particles within 600 s; d1: none lasting over 10 s; d2: fails d0/d1.

Class E can only receive d2, and A1 carries no suffix. For floorings, smoke is only s1 or s2 and there is no droplet code.

Using this when buying

  • For ceilings, partitions and escape routes, choose the highest practical class (A1 or A2-s1,d0) as the designer and local rules require.
  • Ask for the laboratory classification report, not just a "fire resistant" claim in a brochure. Check that the class applies to the same thickness and installation method.
  • Do not confuse reaction-to-fire classes (A1, B-s1,d0) with fire resistance in minutes (EI 60 and so on).
  • For floors, look for the "fl" suffix, for example Bfl-s1.

homeX, an integrated building materials and furniture platform in Indonesia with showroom, warehousing and delivery services, can help compare technical documents for boards, panels and insulation across brands.

Reaction to fire class: related articles and products

FAQ

What does A2-s1,d0 mean? Very limited combustibility (A2), low smoke (s1) and no flaming droplets or particles during the 600-second test (d0).

Is class A1 the same as 2-hour fire resistance? No. A1 is a material reaction-to-fire class; fire resistance in minutes is assessed for complete constructions under a different classification.

Which materials are A1 without testing? Under the European Commission list, mineral wool, cement, glass, ceramics and their products with under 1% organic content can be classed A1 without testing.

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Sources: Measurlabs, EN 13501-1 fire classification (updated 27 Feb 2026); Promat, Combustibility groups and classes (accessed 3 Nov 2026)