Intumescent seals: Signed, sealed and delivered

By Promat 14/11/2018

Educational Article
intumescent seals and fire doors
intumescent seals and fire doors

Promat UK’s Ian Cowley, Regional Director (UK & Scandinavia), highlights why intumescent seals are critically important for fire rated doorsets to provide assured protection for lives and assets.

With fire doors under close scrutiny in the aftermath of Grenfell, the public’s trust in their ability to protect lives and assets urgently needs to be restored. Rebuilding confidence in fire rated doorsets needs a focus on every element of its construction, with one of the most critical elements being the intumescent seal.

Intumescent seals have now been used in fire rated doorsets for four decades. They help to stop the spread of fire and smoke, with the most common types in the UK being manufactured from compounds of sodium silicate or intercalated graphite. These seals will expand to fill the gaps between the door leaf and the frame in the event of a fire, triggered by the rising temperature from a fire. Different base materials, the thickness and whether the seals have been manufactured through extrusion or lamination all determine the level of protection.

Intumescent seals typically represent only 2-3% of the overall materials cost in manufacturing a fire rated doorset, yet these vital fire and smoke stopping products are all too often treated as a commodity which requires little attention and ‘cheapest will do'. After all, as long as a supplier can provide test evidence to show the intumescent seal will deliver on its promise, what’s to be gained by choosing a product that is more expensive? 

The answer comes down to how much we value long term assurance, avoiding future call-backs and providing peace of mind. Building owners, managers and users will have seen the news headlines about fire doors failing to live up to expectations and will rightly be seeking greater certainty in the event of a fire. So, is it worth risking a critical product that is not necessarily the best performing solution, supplied via a complicated, multi-stage supply chain, which makes tracing the original manufacturing source difficult at best, and impossible at worst? Whilst every business has to keep raw material and component costs in check, penny pinching on low unit cost items like intumescent seals seems incomprehensible given the potential for catastrophic consequences.

What to look for in an intumescent seal

The type of intumescent seal used in the fire rated doorset’s construction will determine how well it will perform in the event of a fire. Intumescent seals must, firstly, stand the test of time to be able to offer reliable protection throughout the door’s service life, putting quality and durability to the fore. Consider the review undertaken by FDIS certificated fire door inspectors in 2015, which found that over 61% of fire doors inspected had problems with fire or smoke seals. That could mean nearly two thirds of all fire doors in the UK are putting lives and assets at risk. Whilst some of this may be down to malicious damage, poor upkeep and maintenance failures, how many are suffering problems because the original seal simply wasn’t up to scratch in terms of being resistant to wear and tear?

The self-adhesive strip that allows for the intumescent seals to be applied easily in the factory, and to stay securely in position over time without peeling off, must also be to a good standard. This is why Promat PROMASEAL® intumescent seals utilise advanced gluing technology, originally developed in conjunction with globally renowned experts at Kaiserslautern University, to deliver strong long term adhesion.

Promat has also undertaken its own independently assessed age testing to predict how its PROMASEAL® intumescent seals stand the test of time. This revealed excellent ageing properties, with assurance that the seal will remain stable and functional for at least 33 years.

Secondly, the type of base material used will determine if the seal needs can be left exposed, encapsulated in plastic or concealed within the door slab. Sodium silicate based intumescent seals are susceptible to moisture so need to be protected, whereas graphite seals do not. But that’s not the only consideration here. The quality of the graphite that is used also makes a difference, which is why it is vitally important to understand the origin of the intumescent seal’s manufacture. For example, Promat manufactures graphite PROMASEAL® seals under strictly controlled conditions, with every single batch of the raw material graphite tested before it is approved for use. This is an important quality assurance step that maintains consistency in performance for the finished seals.

A third factor is the difference between an extruded product and a laminated product. Extruded intumescent seals expand in all dimensions once they start reacting to heat, whereas a laminated seal can be designed to expand more controllably in two dimensions. The design of the doorset, therefore, needs to account for this. Promat offers maximum supply chain traceability by manufacturing, processing and laminating in-house, with its UK facility in Heywood equipped with an intumescent guillotine and laminating machine to produce solutions that are tailored to the end user requirement.

As with every type of insulation, different intumescent seals will offer different performance levels. Choosing a lower spec and cheaper product may not always be the most cost-effective route, as a higher performing product may allow for the thickness of the seal to be reduced. This can help with aesthetics and offers a win-win – a better quality intumescent seal without any additional cost.

No margin for error

Whilst the public enquiry into Grenfell continues, it is inevitable that more shortcomings in the building design, construction, maintenance and safety strategies will come to light. In the meantime, it makes complete sense for anyone involved in the manufacture and installation of fire protection products to review their sourcing and specification of raw materials and components, as well as their production processes. Remember, however, that if any changes are made to a doorset’s specification, re-testing of the complete doorset will be required.

Plenty of technical guidance is available from Promat to ensure the most effective fire rated doorsets can be achieved. Promat is already well known in the UK door and window marketplace for its fire resistant glazing products and PROMATECT® H calcium silicate door cores, but it is also one of the global leaders in the manufacture of intumescent seals, being the company that invented graphite based intumescent seals in the 1970s, and today it serves door manufacturers and OEM's across the globe.