Adexon’s breakthroughs in real-life fire and smoke performances continue to leave the rest behind. With a mission built on ‘improving the real-life performance’ of fire and smoke curtains, Adexon continues to redefine expectations and performances in the industry.
Smoke control performance on fire curtains is no different.
For years, fire curtain manufacturers have marketed their products as offering effective smoke protection, but in truth, most have relied on a nuance of the fire door smoke test together with a lack of awareness in the market as to what ‘Sa’ really is. The result? A proliferation of fire curtains with notional smoke ratings that simply don’t hold up in real-life fire scenarios.
At Adexon, we’ve been reviewing all performance aspects of fire curtains during the last ten years, with a ‘blank canvas’ approach; nothing is going to be retained just because “we’ve always done it that way”, or because “the market keeps buying it”. Instead, we are stripping everything back to component level and validating everything by how it will perform in real-life in the situations our customers are buying the products for. We validate everything by testing and independent valid third-party certification, including the extensive use of EXAPs for any dimensions too large for the furnaces (this is a mandatory requirement under the European system of standards and Classifications that the UK is moving towards).
Here’s why no one else comes close.
The Cold Truth About “Cold Smoke” Seals
Although the ‘Sa’ Classification (‘a’ = ambient/ 20°C i.e. cold smoke) is commonly requested on fire doors and hence fire curtains, it is not a sufficient Classification for the latter as there are no intumescent seals in fire curtains (there are on fire doors). As such, fire curtain products that ‘pass’ low/ cold temperature testing are sold in the market despite the reality that they won’t provide smoke protection when exposed to the temperatures of a fire.
The industry standard for many fire curtains has long been the use of cold smoke seals. These are typically made from polypropylene filament, which melts at 171°C. While this may work in a cold smoke scenario (under 171°C), a real fire rapidly exceeds this temperature — often within seconds – and that is a major potential problem.
Cold smoke seals were originally designed for fire doors, where they complement intumescent strips (which activate at around 180°C). But fire curtains don’t function like hinged fire doors. You can’t use intumescent seals on curtains, because if they expand too early, before the curtain descends, they could block the system from closing altogether. In short: fire curtain manufacturers have taken one half of a system designed for fire doors and have used it on fire curtains leading to the aforementioned outcome: fire curtains being sold with ‘smoke’ certification but that won’t provide the smoke protection the buyer is looking for.
Commonly, ‘Sa’ is the smoke performance Classification stipulated in specifications and fire strategies. Yet, ‘Sa’ for fire curtains is insufficient; purchasers are not getting what they think they are buying. Purchasers think they are getting a fire curtain that will give them smoke protection – in a fire – when they buy a fire curtain that has the ‘Sa’ smoke Classification. In reality, they are not necessarily getting a fire curtain that will give them smoke protection – in a fire – when they buy this. The cold smoke seals frequently used on fire curtains melt within seconds when exposed to the heat curve of the test furnace (designed to simulate a real-life fire). This means that fire curtains that use cold smoke seals to achieve ‘Sa’ smoke Classification (ambient temperature [20°C] smoke) provide only seconds of smoke protection in real-world fire temperatures. Adexon have long since said this is simply not good enough, especially in a post-Grenfell fire industry that is endeavouring to change its ways.
Cause & Effect
So how did ‘Sa’ become the norm in specification and fire strategies for fire curtains? We believe there are two factors contributing to this:
- because it is the norm on fire doors (which are, however, dual protected i.e. intumescent seals activate at 180°C when the cold smoke seals melt); and
- because fire curtain manufacturers have been happy to say ‘it is ok on fire doors so [because we can’t do anything better], it is ok on fire curtains’.
This latter point is not in the best interests of life-safety.
At Adexon we have only used fire resistant materials for smoke sealing for a number of years and have more recently introduced the first ‘Sa4’ and ‘S200’ smoke Classified fire curtains. More on this below.
Optimising Performance with EN 1634-3 Smoke Test Parameters
The EN 1634-3 smoke test permits smoke leakage of 3m3/linear metre of door perimeter excluding the threshold (per hour at the pressure differential)
e.g., a 2m high x 1m wide door would pass the test so long as the total smoke leakage did not exceed:
(2+2+1 [don’t add the width at the bottom/ threshold]) x 3m3 = 5 x 3 = 15m3 per hour (at the pressure differential)
This can be taken to say the threshold sealing is not to be tested because the leakage measurement excludes the threshold in the calculation for a ‘pass’. In real-life, smoke leakage anywhere can be fatal. Indeed, over 70% of fatalities and injuries are due to hot smoke and gases. What we know is that fire curtains with the simple Sa Classification are only tested on three sides and we are aware of fire curtain manufacturers taping the threshold down to ‘pass’ the test – because ‘you don’t need to measure the threshold leakage’.
It was never intended by the authors of the test that smoke could be allowed to pour through the product at the threshold. Hinged fire doors are different to fire curtains, the latter having no threshold or bottom seals.
Due to this nuance of the smoke test, we advocate for Sa4 Classification as a minimum (all four sides tested) on fire curtains. However, we strongly recommend S200 Classification being used which then eliminates smoke sealing materials with low temperature melting points from being used.
Not testing the threshold allows ‘architectural’ metal bottom bars (usually T- or triangle-shaped profiles) on the market that are meant to provide smoke performance in a fire. However, whilst these metal bottom bars look sleek they do not provide the requisite smoke performance.
Metal does not make a reliable seal on solid surfaces, that’s why entire industries exist just to design flexible sealing solutions.
The Adexon Difference: Certified Performance, All Four Sides
We’ve engineered a system that solves the problem of bottom-edge smoke leakage, and much more.
Adexon’s proprietary high-performance flexible bottom sealing bar is the first of its kind. Integrated into our fire curtain systems, it achieves true Sa4 smoke classification, tested and certified on all four sides. No tape. No cut corners.
Even better? Our system also meets S200 smoke Classification, meaning it performs under elevated-temperature smoke conditions. That’s smoke at 200°C, the kind that’s far more representative of a real fire.
And it’s not just lab performance, our curtain seals function reliably on uneven floors, sloping thresholds, and ramps, areas where traditional systems are not tested and should not be used.
Raising the Bar for the Entire Industry.
At Adexon, we believe certification is a prerequisite – a bit like a valid MOT and insurance on your car – but it only really matters when, above and beyond the tick boxing, it reflects what happens in the real world. That’s why we design, test, and certify for the unpredictable, not just the test bench.
If your project demands a smoke-rated fire curtain that actually seals, the choice is simple. Choose the system that leads the market in performance, design integration, and real-world reliability.
Choose Adexon.