Passive Purple Fire Performance: Class A in the US, Euroclass C (and B-s1,d0 with FRED)
Fire performance you can specify with confidence 🔥
Airtightness and fire safety are often treated as separate conversations. With Passive Purple, they don't have to be. Our liquid-applied airtight and vapour-control membrane carries genuine, independently tested fire classifications on both the North American and European systems — something rarely seen from a liquid airtight coating.
This post explains what those classifications actually mean, and where the Passive Purple + FRED system can take you when a project demands more.
The US picture: ASTM E84, Class A
In North America, surface burning of building materials is assessed under ASTM E84 — the "Steiner tunnel" test. It produces two numbers:
- Flame Spread Index (FSI) — how quickly flame travels across the surface.
- Smoke Developed Index (SDI) — how much smoke the material generates.
A Class A rating — the highest interior finish classification — requires an FSI of 25 or less and an SDI of 450 or less. Passive Purple doesn't just scrape in:
- Passive Purple: Flame Spread Index 0, Smoke Developed 55
- Passive Purple Brush: Flame Spread Index 0, Smoke Developed 35
Both are comfortably Class A, tested by ICC NTA in the USA. Passive Purple is certified as a Class A interior finish in ICC-ES ESR-4715 — the evaluation report specifiers and code officials rely on.
The European picture: EN 13501-1 and the Euroclass system
In Europe, reaction to fire is classified under EN 13501-1 using the Euroclass system. The main letter grades run A1, A2, B, C, D, E, F — A1 being non-combustible and the grades stepping down from there. Two suffixes add detail:
- s — smoke production: s1 (very low) to s3 (substantial).
- d — flaming droplets/particles: d0 (none) to d2.
So a classification like C-s1,d0 tells you the reaction-to-fire grade, that smoke is very low, and that there are no flaming droplets.
Passive Purple alone is classified Euroclass C-s1,d0, tested by Exova Metech. For a liquid airtight membrane, that is a strong result — and the s1,d0 suffixes matter as much as the letter, because in a fire, smoke and burning droplets are what threaten escape routes.
Pushing further: the Passive Purple + FRED system 🛡️
Where a project calls for a higher grade, FRED — a separate white intumescent fire-protection topcoat — is applied over Passive Purple. As a system, this achieves:
- EN 13501-1 Euroclass B-s1,d0
- Classified by PAVUS a.s. (Czech Republic, Notified Body 1391)
- Report reference PK1-01-25-014
- Retaining s1 (very low smoke) and d0 (no flaming droplets)
- Valid on A1 substrates with a density of ≥653 kg/m³
An important distinction for specifiers: the B-s1,d0 classification belongs to the Passive Purple + FRED system. Passive Purple on its own is Euroclass C-s1,d0 — we never claim otherwise. FRED is what lets you lift the build-up to Class B where the specification requires it.
Low heat release, too
Beyond the headline classifications, cone-calorimeter testing to ASTM E1354 (by Intertek) measured Passive Purple's total heat release at just 6.29 MJ/m². Heat release is a direct measure of how much a material contributes to a developing fire — and a low figure means Passive Purple adds very little fuel to the load.
Why this matters
It is unusual for a liquid airtight membrane to carry robust, independent fire classifications on both the US (ASTM E84 Class A) and European (EN 13501-1 Euroclass C-s1,d0) systems. That dual coverage makes Passive Purple straightforward to specify whichever regulatory framework a project sits under — and where a higher grade is needed, the Passive Purple + FRED system reaches Euroclass B-s1,d0.
One continuous coating, airtightness and vapour control, backed by fire data that stands up to scrutiny.
Specifying Passive Purple? Review the full test data & certifications for the complete reports and classifications referenced above.