Fire Ratings Explained: B1, A2, Class I and What Buyers Actually Need

Fire rating is the most quoted and least understood line on a wall panel specification sheet. Suppliers write B1 because it sounds reassuring, buyers in the Gulf ask for Class A, American contractors ask for Class I, and European specifiers want A2-s1,d0. These labels come from three different test regimes with different scales, different specimen sizes and different pass criteria. Treating them as translations of each other is how projects get rejected at inspection.

The three systems, in one paragraph each

GB 8624 (China)

China classifies building materials as A (non-combustible), B1 (flame retardant), B2 (combustible) and B3 (flammable), with A further split into A1 and A2. GB 8624-2012 aligns its A2, B and C classes with the European test methods, so a Chinese B1 panel tested to the harmonized method corresponds roughly to EN class B or C depending on the additional sub-classes for smoke and burning droplets.

EN 13501-1 (Europe)

The European system uses a letter plus two sub-classes: A1, A2, B, C, D, E or F, then s1-s3 for smoke production and d0-d2 for flaming droplets. A typical flame-retardant PVC wall panel lands at B-s1,d0 or C-s1,d0. The tests behind it are EN 13823 (SBI, room corner) and EN ISO 11925-2 (single flame source).

ASTM E84 / UL 723 (North America)

The American system reports two numbers: Flame Spread Index (FSI) and Smoke Developed Index (SDI), on a 0-200+ scale from the Steiner tunnel test. Products are grouped as Class A (FSI 0-25), Class B (26-75) and Class C (76-200). A 25/450 result is a different product from a 10/50 result even though both are Class A.

Rough comparison, not equivalence

These columns are indicative only. A GB B1 report is not accepted as evidence of EN B-s1,d0 or of ASTM Class A. If a project requires a specific class, the product must be tested to that specific standard, on a specimen of the same thickness and construction.

Where each rating is actually required

• China: GB 8624 classifications are mandatory under GB 50222 for interior decoration. Corridors and escape routes in high-rise buildings commonly require B1 or better; some public assembly areas require A.
• Europe: EN 13501-1 classes are required by national building regulations, and for CE marking under the harmonized standard EN 15102 for wall coverings. Escape routes and high-rise lobbies commonly require B-s1,d0 or better; s1 smoke class is often the requirement that actually rejects a product.
• United States: IBC requires Class A or B interior finishes depending on occupancy and sprinkler status. Wall panels in corridors of hotels and healthcare buildings almost always need Class A with SDI under 450, and often a separate NFPA 286 or ASTM E84 assembly test if the panel is used as a finish over a substrate.
• Middle East and Southeast Asia: Often follows a mix of British, ASTM and local civil defense rules. Saudi and UAE projects frequently specify ASTM E84 Class A plus a civil defense approval, and increasingly require NFPA 285 for exterior assemblies.

Why two B1 panels can behave differently

Flame retardancy is a formulation question. Adding 5-15% of ATH or a brominated system changes the reaction to fire, but it also affects cost, color, flexibility and density. Three consequences matter to buyers:

1. FR compound usually costs USD 0.15-0.60 per m2 more at the panel level, depending on loading level.
2. High FR loading can make white panels look slightly yellow, which is why some factories keep two formulations: FR for corridors, non-FR for feature walls.
3. The rating is thickness-specific. A 5 mm panel and a 9 mm panel from the same line need separate test reports.

How to verify a fire report in ten minutes

1. Check the report header: testing laboratory name, accreditation mark (CNAS, UKAS, IAS, or similar), report number and date.
2. Check the specimen description: material, thickness, density, construction and whether it was tested with or without a substrate.
3. Check the test standard and edition, for example EN 13823:2020 or ASTM E84-23.
4. Check the result line, not the marketing line: B-s1,d0 with a date, or FSI and SDI numbers.
5. Check the report holder. If the holder is not the supplier you are buying from, ask for the authorization letter from the report holder.
6. Look for the expiry. Many laboratories issue reports with a validity period, commonly 1-3 years if the formulation is unchanged.
7. Verify on the lab website using the report number. It takes two minutes and eliminates the most common sourcing fraud in this category.

What to write into the purchase order

Specimen details buyers routinely miss

Two reports can carry the same class and still describe different products. Check the mounting and fixing method: a panel tested free-standing, glued to a calcium silicate board, or mechanically fixed to a steel frame behaves differently in a fire, and the construction that was tested is the only construction the report supports. Check the substrate, since many panels only achieve their class over a non-combustible backing, and check whether the panel was tested with joints, because the gap between panels is where flame spreads in real installations. If your site uses a different fixing system or a different substrate, the certificate may no longer apply, and an inspector who reads the report will say so.

Fire class and insurance

There is a commercial reason to take fire documentation seriously beyond the building permit. Property insurers increasingly ask for evidence of the installed finishes in commercial interiors, and a claim after a fire can be reduced or refused if the installed product does not match the declared class. Where a project mixes a rated panel in the corridor with an unrated panel in the office, keep the two clearly separated in the drawings, the invoices and the packing list, so the evidence trail matches the installed condition. It costs nothing to do this at order stage and is very expensive to reconstruct after a loss.

Practical advice for trade buyers

Ask early which class the project needs, because it changes both price and lead time. A non-FR PVC panel might be USD 3.80 per m2 while the FR equivalent is USD 4.20-4.60, and the FR grade may add 5-10 days to production. If the project spans several floors with different occupancies, buy the higher class for the whole order rather than mixing batches - it keeps the job simpler and avoids the ceiling-versus-wall argument at inspection.

Finally, remember what a fire rating is not. It is not a warranty that the assembly passes a full-scale test, and it is not a substitute for correct installation over a compliant substrate. Most failures on site come from the wrong substrate, missing fire stops, or a panel installed with a combustible adhesive, none of which the report covers.