Fire Classes Explained: A1, A2-s1,d0 and EI 30-60-90
A commercial project will ask you two different fire questions, and confusing them buys the wrong material. The first is how a material reacts to fire (A1, A2-s1,d0…). The second is how long a built element holds fire back (EI 30, EI 60, EI 90). Different things, different certificates.
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Reaction to fire: does the material burn?
This class describes the material itself. The European system runs from A1 to F; A1 does not burn at all, F is simply unclassified.
The suffixes matter as much as the letter. "s" is smoke production (s1 is the lowest) and "d" is flaming droplets (d0 means none). Because most fire deaths come from smoke rather than flame, s1 is a critical requirement in practice.
| Class | Meaning | Typical material |
|---|---|---|
| A1 | Non-combustible, no contribution to fire | Stone wool, mineral ceiling tile, steel |
| A2-s1,d0 | Negligible contribution, very low smoke, no droplets | Gypsum board |
| B-s1,d0 | Very limited contribution, low smoke | Some finishes and laminates |
| C / D | Noticeable contribution | Timber-based products, some finishes |
| E / F | High contribution / unclassified | Unprotected polystyrene foam |
Fire resistance: how long does the element hold?
EI codes describe a built element — a wall, a ceiling, a door — not a material. The number is minutes.
E is integrity: flame and hot gas do not pass to the other side. I is insulation: the unexposed face does not reach a dangerous temperature. EI 60 means that wall holds back both flame and heat for 60 minutes.
The critical point: an EI class belongs to a certified system, not to individual products. If the certificate's stud spacing, board type, layer count, screw spacing and cavity infill are not reproduced exactly, the class does not apply.
- EI 30 — 30 minutes: escape corridors, some partitions.
- EI 60 — 60 minutes: floor separations, common-area boundaries.
- EI 90 / EI 120 — plant rooms, fire compartment walls.
What sets resistance in a drywall system?
Gypsum performs in fire because of the water chemically bound in its crystal structure. As it heats, that water drives off and the board holds the temperature steady for a period while protecting the structure behind it. This is why layer count translates directly into minutes.
Fire-rated boards (usually pink or red) carry glass fibre reinforcement in the core so the board stays intact rather than crumbling under heat.
Mineral wool infill is not only acoustic: in most EI-certified wall build-ups the infill is a required component, and removing it lowers the class.
What to ask for in practice
Residential projects rarely carry a specific requirement; standard gypsum board is already A2-s1,d0, meaning its contribution to a fire is negligible.
On a commercial project, ask for this: the certificate number of the system being installed, and the exact build-up that certificate covers. "We used fire-rated board" is a sentence, not a document.
In short
- Reaction to fire (A1, A2-s1,d0) describes a material; fire resistance (EI 30/60/90) describes a built element.
- The s1 and d0 suffixes matter as much as the letter — smoke and burning droplets are the real hazard.
- An EI class belongs to a certified system; change the build-up and the class is gone.
- Gypsum performs because of its crystal water; layer count converts directly into minutes.
- On commercial work ask for the certificate number and the build-up, not a reassurance.
