The science behind cold smoke seals

Melts at 170C… 🫗

Auto-ignites* at 200C… 🔥

(*spontaneously catches fire without a direct source of ignition)

Do you want this to ‘protect’ you from hot smoke and gases in a 1,000C fire?


The image shows the chemical formula illustration for the hydrocarbon commonly known as polypropylene.

Cold smoke seals are a filament brush strip that is manufactured from the polypropylene hydrocarbon.

We’ve had a lot of questions over the years as to why fire curtains ‘get away’ with using cold smoke seals WITHOUT intumescent strips.

On a fire door the cold smoke seals melt at 170C and the intumescent seals kick in at 180C meaning continuous smoke seal protection in a fire. This is how sealing on a fire door works (in simple terms) 📈

What about fire curtains?

Fire curtains cannot use intumescent strips for fear of blocking deployment of the fabric, so how do they get away with using cold smoke seals on their own?

The answer is, IN THE TEST they ‘get away’ with it because the smoke test (BS EN 1634-3) is still only a cold smoke test. In real life they don’t.

The current smoke test is not a true reflection of a real fire and one day it will be changed to a hot smoke test (our hope and view 🤞)

The point of this post? You may want to consider using fire curtains that only use fire resistant materials and components to protect you from smoke in a fire. They are available (without cold smoke seals).

These fire curtains are still only tested in the cold temperatures that the standards call for, but which would you prefer?

Read more, here.

And are you wondering what happens to the cold smoke seals on fire curtains on the non fire side?

Going by the heat curve in BS EN 1363-1 we can see the temperature in a fire test is 576C after just 5 minutes. Polypropylene auto-ignites at circa 200C. What happens to this flaming on the non-fire side? What else catches alight on the non-fire side as a result?