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Fire curtains act as flexible barriers to prevent the spread of smoke and flames through a building during a fire. To be effective, these curtains need to fill the area that they are designed to block completely, without leaving any gaps around the edges. Fabric retention is a key design element in achieving this objective.
When a fire curtain is in place during a fire, the sides of the curtain each sit within a guide – a housing through which the fabric slides as it is deployed. These guides are meant to hold the curtain in position, even if there is air movement caused by temperature and pressure differences on each side of the curtain.
However, problems can be encountered with these guides in some products, including:
- Curtains jamming in the guides during deployment.
- Curtain fabric coming out of the guides.
- Fabric tearing at the edges.
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 consequences for occupants trying to escape the building.
Why does this happen?
The main culprit is the fabric retention design of the fire curtain. The majority of manufacturers use either poppers, or nuts and bolts to retain the edge of the fabric inside the guides (Figure 1). Because these fittings are wider than the guide aperture the fabric travels through, they should keep the edges of the curtain secure and maintain the integrity of the curtain as a barrier to flames and smoke.
Figure 1: Typical examples of fabric retention using poppers or nuts and bolts
However, we have seen many examples of installed curtains where this design fails to deliver the required performance (Figure 2). The holes in the curtain caused by the bolts or poppers create areas of weakness in the fabric, and all too often this causes tearing if any resistance is encountered during the deployment of the curtain. In addition, the retention is not continuous, which means that it is possible for the edge of the curtain to become disengaged from the guide at certain locations.
A dangerous ‘solution’
As bad as these problems are, still worse 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 obstructions inside the guide. This issue can occur as early as initial commissioning prior to handover of a curtain to the customer, or during annual servicing when the curtain is tested.
There is an easy solution, of course – remove the troublesome poppers or bolts so that the curtain descends smoothly, right? Obviously, this is not a solution at all, but in fact a highly dangerous and illegal practice. Illegal because a fire safety product is being tampered with, and dangerous because there is a much higher chance that the fabric edges will blow out of the guides due to air currents and render the curtain much less effective.
Sadly, because of the prevalence of this design, it is likely that most of the fire curtains currently installed are at risk of experiencing these serious issues with fabric retention.
Is there an alternative?
Thankfully, yes there is. Adexon have pioneered a simple yet highly effective design which uses a steel rod that runs along the entire length of the guide, and is fully integrated within it (Figure 3). 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 is able to 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.
Adexon’s design avoids the potential tearing issues with the popper and nut and bolt designs, and there is very little chance of any maintenance or repair of the curtain fabric being needed 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 design which you can read more about here.
Adexon believes that fabric retention is an issue that no-one can afford to ignore if they have fire curtains installed in their building. The HSE, police and fire service will not look upon building owners as innocent victims when investigating if their obligations under the Regulatory Reform (Fire Safety) Order 2005 have not been met with respect to safety equipment. Can you be sure that your fire curtains are going to work when needed, or that they have not been tampered with to allow them to deploy without jamming?
To help put your mind at rest, we are offering a free, no-obligation inspection of your fire curtains and we’ll provide a report detailing their design and any potential actions we would recommend.