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. The ASTM E84 test reports are available to specifiers and code officials on request.
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.