Seal of Approval

08/01/2020
When is a fire door not a fire door? When it has the incorrect seals fitted – or none at all! Who has responsibility for enduring that seal selection is correct and compliant? MD, Michael Spoors, answers some questions about that they are asked most frequently about fire door seals.

Q. Do all intumescent materials activate at the same temperature?
A. No. The various types activate at different temperatures, therefore only the same material that was used in the actual fire test should be fitted. Activating too early or too late is likely to compromise the test evidence for the fire door.

Q. Can I substitute a different material to that fire tested?
A. No. Because there are different activation temperatures and different pressures and degrees of expansion, you should only use the same type of seal as that which was tested. Using a different seal could have serious consequences on the door’s fire performance. For instance, if the wrong seal was used down the meeting stiles of a pair of doors it can expand with such force that the door leaves push open, and the door fails.

Q. Is there such thing as a 30 minute fire seal?
A. Not all fire doors are the same. Make sure that you have a properly tested fire door construction. Norseal will happily provide the test evidence on a data sheet so that you can check within that data what type and size (or sizes) of seal have been tested and that is what you should specify and supply. Remember that adding a fire seal to any door doesn’t automatically make it a fire door.

Where door manufacturer’s test evidence isn’t available, the usual recommendation is to use a 15 x 4mm seal, fitted centrally at the head and both jambs of a single leaf, single acting door. If it’s a fire and smoke door (which will be denoted FD30S), then a fire seal alone will not be sufficient – you must purchase combined or separate smoke and fire seals.

Q. I have an existing fire rated door but have been told it needs to be upgraded to provide smoke containment too. What do I do?
A. The simplest way of achieving this is by installing a tested retrofit cold smoke seal. There is a choice of sizes for different applications, including ultra-low frictional resistance for ease of door operation, and as they fix straight onto the doorstop with strong self-adhesive tape, it’s easy to install and you won’t need to remove the door to fit it. If you have double leaf doors, it will need a seal at the meeting stile too.

Q. What’s the difference between a brush seal and one with flexible fins?
A. Brush seals were the first on the market back in the 1970s, hence they have popular appeal as the traditional smoke seal solution. While they’re still effective as smoke seals, the Building Regulations now have requirements for doors to also provide acoustic containment and be easy to operate to allow access for all. With these requirements, the brush-style smoke seal is sometimes not up to the job. Brushes are particularly poor at providing acoustic containment, as the filaments allow air to pass straight through, and where air goes – sound goes too. They also provide plenty of friction, which makes doors more difficult to operate. Fin-style seals provide a much more comprehensive and hygienic solution. They have better acoustic containment properties (particularly ones with multiple fins) and much lower frictional resistance.

It’s important that the fin seal remains continuous around ironmongery for both acoustic and smoke containment. Offset fins make this much easier.

Q. Can you paint over fire and smoke seals?
A. Over-painting of intumescent seals would not compromise performance in a fire situation. However do not paint over the flexible elements of smoke seals as this will certainly compromise smoke containment performance. If the smoke seal part of the seal has already been painted over, replace it.

Q. I’m working on a hospital project that needs a sealing system that will stand up to rigorous cleaning. What do you recommend?
A. There are perimeter and threshold sealing products available with carriers and gaskets which are impervious to most strong cleaning chemicals, making them ideal for hospitals. Where smoke protection is needed, fins will harbour much less dust and dirt than brushes and are easier to wipe clean. Some products are available with anti-microbial additives, which might be an advantage. Check with us for details.

Q: Approved Document M says that doors need to be easy for everyone to use. Which products do I choose?
A: Leading brands have been designed with ease of access in mind, and the recommended seals would provide exceptionally low frictional resistance to ensure the seal interferes as little as possible with the smooth operation of the doorset.

Considerations include:

• For a combined acoustic, smoke and fire sealing solution, choose a one-seal solution, which carries test evidence and third party accreditation. Remember that brush-style fire and smoke seals provide very high levels of frictional resistance, so won’t be suitable.
• For acoustic and smoke containment only, either for new door assemblies either fit a surface mounted, self-adhesive, retrofit seal or alternatively, an architectural perimeter seal mounted onto the doorstop, will provide a compression seal that will provide minimal interference.
• It’s vital to have a seal at the threshold for effective acoustic and smoke containment, and good automatic threshold drop seals have been designed with high efficiency mechanisms, so doors can be opened with the minimum of effort.
• There are also a number of threshold ramps available for situations where different floor levels need to be accommodated.

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