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Active fire curtains serve as flexible barriers that effectively prevent the spread of smoke and fire through a building during a fire.
For fire curtains to fulfil their intended purpose when deployed, they must provide a tightly sealed barrier across the opening they are assigned to obstruct, without any holes or gaps. Complete integrity of the barrier is essential for it to perform as designed and tested.
Active fire curtains deploy much in the same manner as roller shutters, with the fire resistant fabric unrolling off the barrel. The fabric is held in place by a side guide channel that retains the fabric on both of its vertical edges. The top edge is attached to the barrel and protected by a casing, and the bottom edge descends to the floor where the bottom weighted rail sits on the floor. The fabric retention is a crucial element in achieving the vital objective.
This article looks into the 3 most common problems encountered with active fire curtains, and includes an introduction to Adexon’s fabric retention design and its potential to enhance fire safety measures within buildings.
When a fire curtain is in place during a fire, the sides of the curtain fabric each sit within a side guide as described above. This channel has a narrow aperture through which the fabric slides as it is deployed (see Figure 1).
The curtain fabric has to be retained in these side guides, even if there is air movement caused by temperature and pressure differences on each side of the curtain. This is typically achieved using one of two different methods. One of these methods encounters frequent problems, with the most common being:
- Curtains jamming in the guides during deployment.
- Curtain fabric coming out of the guides.
- Fabric tearing.
The effect of all these issues is that the curtain’s integrity as a barrier is compromised at best, and may be rendered completely ineffective at worst, with potentially deadly and devastating consequences.
Why do problems sometimes arise with fire curtains?
The root cause of the above problems can be traced back to an old design of fabric retention that is still used by some fire curtain manufacturers. This old design uses either poppers, or nuts and bolts, to retain the edge of the fabric inside the guides (Figure 1).
Because these poppers or bolts are wider than the aperture in the side guide, the fabric is retained whilst being free to travel up and down the guide This should keep the edges of the curtain secure and maintain the integrity of the curtain as a barrier to flames and smoke.
However, we have seen many examples of installed curtains where this design fails (Figure 2).
The holes punctured in the curtain fabric by the bolts or poppers create a weakness in the fabric which leads to tearing and ripping under normal use or when resistance is encountered during the deployment of the curtain.
In addition, the retention is not continuous, which means that it is possible for sections of the edge of the curtain to come out of the guide at certain locations.
Curtain jamming, and worse
As bad as these problems are, the biggest headache is the jamming of the curtain in the guide as it deploys.
Poppers and nut/bolt heads are not designed as moving parts, and can easily catch on surfaces or in the narrow aperture of the guide. This issue can occur as early as initial commissioning prior to handover of a curtain to the customer, or during servicing and even weekly testing.
This creates serious concern and frustration with customers.
If the troublesome poppers or bolts are removed, this serious issue can be ‘overcome’, so the curtain descends smoothly.
Whether this happens intentionally, or as a result of frequent jamming and the resultant stress on the fabric, or as a result of someone pulling on the curtain to ‘help’ the curtain pass the jamming point, these poppers and bolts can ‘go missing’ as seen in Figure 1.
For someone to deliberately remove the poppers or bolts would be a highly dangerous practice that would probably be deemed illegal (because a fire safety product is being tampered with) but whichever of the ways these poppers or bolts ‘go missing’, it is highly dangerous. This is because there is now a much larger section of fabric that can come out of the guides and thus allow fire and smoke to pass through.
Due to the prevalence of this old design, a high percentage of the fire curtains currently installed in the UK are at risk of experiencing these serious issues with fabric retention.
The permanent solution that works
This rod is fixed at the bottom of the guide in a slotted steel plate. The fabric is hemmed around the rod and slides along it as the curtain deploys.
Once in place, the rod can move back and forth along the slotted plate as needed to accommodate movement of the fabric due to air currents or a pressure gradient.
This relieves tension in the curtain without any chance of the edges of the fabric coming away from the guides.
‘Genius’ smoke seal design
Adexon’s design avoids the potential tearing issues that occur with the old popper and nut/ bolt designs, and there is very little need for maintenance or repair of the curtain fabric during regular service inspections.
This reduces the cost of maintenance and the risk of a curtain being inoperative while repairs are carried out.
This innovative arrangement is also a key element in our state-of-the-art smoke seal design1.
We were asked many times at The Fire Safety Event and at Firex, “Who is the genius [behind the design]?” It is simple but brilliant.
Fabric retention is an issue that cannot be ignored
Adexon believes that fabric retention is an issue that no-one can afford to ignore if they have fire curtains installed in their building.
When carrying out investigations, the HSE or BSR will not overlook the legal requirements of the Responsible Person under the Regulatory Reform (Fire Safety) Order 2005 to have life safety equipment maintained and in good working order.
If you are not sure that your fire curtains are going to work when needed, or if you are not sure if they are in the good working order as tested and installed, it is advisory to have them checked by an industry leading specialist that can tell you what you need to hear.
To help with this, Adexon are offering a free, no-obligation inspection of your fire curtains which comes with a follow-up report detailing any potential actions required.
This article was written in October 2022 by the team at Adexon Fire & Smoke and revised on 9th June 2023. It includes the views of the Adexon team and its intention is to raise awareness and standards in the fire safety industry.
If you have a question for the team or would like to give feedback on this article or find out more, please get in touch.