BS 8524-1: A conflicting national standard that should be formally withdrawn – and the improvements it needed.

Important Note – these points are made despite the fact BS 8524-1 is a conflicting national standard that should be formally withdrawn.

Table of Contents

1. Introduction

If you are familiar with BS 8524-1:2013 here are some of the more significant improvements it needed.

The format we have used is the format used when commenting on the DPC version of the standard (the Draft for Public Comment). This will make it easier reading for those familiar with the standards, and hopefully will make easy reading for those new to the process.

2. Foreword

Comments:

The words ‘barrier assemblies’ are superfluous descriptors and unnecessarily adding complexity without adding anything of value.

Proposed changes:

Fire curtains should be called fire curtains. Add the word ‘active’ to differentiate from static fire curtains, and differentiate by type (vertical, horizontal, concertina) but anything else is over elaborate. Complexity is solved with simplicity, not more complexity.

3. Scope

Comments:

From the definition of conflicting standards, BS 8524-1 conflicts with BS EN 16034. They are both for the manufacture, and fire and smoke performances, of fire curtains. They both have the same fire test (BS EN 1634-1), the same smoke test (BS EN 1634-3) and the same cycle test. Differing the content and substituting words (semantics) is not sufficient to make BS 8524-1 a non-conflicting standard with BS EN 16034. If BS 8524-1 and BS EN 16034 are deemed to be not conflicting, is there an example of two standards that are deemed conflicting, and can we be shown how they are materially different in similarity to these two?

Proposed changes:

BS 8524-1 should be formally withdrawn as stipulated in the foreword of the harmonised standard BS EN 16034, “This European Standard shall be given the status of a national standard… and conflicting national standards shall be withdrawn at the latest by October 2019.”

Alternatively, the scope of BS 8524-1 should specifically exclude vertical fire curtains and should point the reader to the legally required harmonised standard BS EN 16034 for vertical fire curtains. This would mean BS 8524-1 could be used for horizontal fire curtains and concertina fire curtains as neither of these types of fire curtains are specifically covered by BS EN 16034.

4. Clause 3.9 fusible link

Comments:

Remove this definition unless someone is proposing using the item in a fire curtain. Standards need to be as succinct as possible, without being inflated with unnecessary wording, clauses, definitions etc.

Proposed changes:

Remove definition.

5. Clause 4.2 Side retention

Comments:

Hard travelling objects in the side-guides should be prohibited from use as a means of fabric retention because they have the potential to move into, and jam in, the side-guide aperture. For example, a nut and bolt or popper should not be allowed to be used to retain the fabric in the side-guides (Figure 1). These hard travelling objects cause sufficiently frequent operational issues to be considered a design flaw and a considerable threat to the life-safety performance of the product in real life conditions.

There are multiple issues with fire curtains jamming every day across the UK, and the issues are traced back to these hard travelling objects in the side-guides.

The problems are so prevalent that some people who have had bad experiences will now only use fire curtains as a product of last resort. Others that have them installed cannot afford to have them replaced so simply do not test them to avoid having them jam; a serious safety issue and a direct legal contravention of the Regulatory Reform (Fire Safety) Order 2005 (FSO 2005).

Fire curtains should be tested weekly along with the fire alarm and other automatic opening and closing fire strategy related products. Where the fire curtains frequently jam in the side-guides an engineer has to be called out to do a temporary repair. A week or fortnight or month later the same can happen again.

A British Standard should advocate for best practice and prohibit designs that have inherent weaknesses that can be catastrophic to life-safety (if the fire curtain jams and doesn’t deploy in a fire it could be catastrophic). Some may argue that they work fine in a test laboratory situation and in ‘most cases’ in real life. Whilst this may be true we need to acknowledge and act on the scenarios that are happening daily. Standards are not created to be a picture on the wall but are created to provide best practice that if followed gives people the highest level of safety and quality possible. Manufacturers don’t have to follow the standards, but standards should not be compromised to suit manufacturers, however big or influential.

There are alternative designs of fabric retention available for manufacturers to use and these are not protected by patent. Apart from the cost of new testing, the only thing stopping manufacturers using a design that works more reliably is commercial pride because they were not the first.

A second frequent issue with using a nut and bolt or a popper to retain the fabric in the side guide is that the fabric penetration leads to a weakening of the fabric together with a point load on that part of the fabric. The combination leads to frequent and well-known tearing of the fabric (Fig. 2). This is such a problem that some have proposed ‘standardising’ on-site fabric repairs in standards such as ISO 21524 and BS 8524.

The first thing to note is that this attempt to standardise repairs is confirmation of the frequency of the issue. In other words, no one can minimise the issue and say that this design of penetrating the fabric with a nut and bolt or popper that serves as the means to retain the fabric in the guide is not causing significant frequency of tearing issues in the fabric.

Secondly, attempting to standardise repairs of fabric on site (which is not good safety practice – see more in the comment on that section of the standard) is not following the Root Cause Analysis principles of ISO9 9001:2015. Instead of recognising the cause of the problem and rectifying that, it is attempting to create a standard way of addressing the symptoms; akin to putting a sticky plaster on an infected wound and replacing from time to time without treating the source of the infection.

Thirdly, there is no way of testing all the variables of tears and respective repairs and there is no way of controlling how well this is done on site, certainly not control measures that are apropos for a life safety product.

An additional problem with the fabric tearing around the retaining bolt/ popper is the likelihood of the bolt/ popper coming loose and falling out (Fig. 3). These retention bolts/ poppers are tested at pre-determined spacing. Removing one bolt/ popper doubles the spacing between remaining bolts/ poppers allowing the fabric to billow and come loose from the guides, enabling the passage of fire and smoke through the fire curtain.

There is more information, and photos, around the issues of allowing hard travelling objects to be used for fabric retention in this article by Adexon Fire & Smoke Curtains, Active fire curtain maintenance – and the 3 reasons fabric retention design matters1.

If we wanted the standard to be world-leading, or even industry-leading, and if we want to restore consumers confidence in fire curtains the below proposed change is a step in the right direction.

If we protect our national manufacturers who use the old designs with poppers and nuts and bolts, we will only fall further behind other nations. On the contrary, if we ‘disrupt’ ourselves by embracing improvements before others do, we can lead the world and be a flag-bearer for quality and safety-leading performances. British standards provide this opportunity to raise the standard for fire-safety.

If manufacturers must improve their products to comply with a standard, the standard has done its job.

Proposed changes:

Prohibit hard travelling objects such as poppers or nuts and bolts from being used in the side-guides as a form of fabric retention. Also, only permit designs that have continuous fabric retention.

There are designs available without patent protection (see example in Figure 4) so any manufacturer can make this simple improvement for life-safety.

6. Clause 4.3.2 The amount of overlap required for assemblies other than the tested size shall be determined in accordance with Annex A and BS EN 15269-11

Comments:

The fabric overlap should increase proportional to the increase in height such that the ratio of overlap to clear opening height is equal to or greater than the ratio in the successfully tested specimen. Referring to existing publications that don’t exceed or match this requirement is to miss this opportunity to introduce a methodical and rigid, rules-based, calculation method.

Proposed changes:

The fabric overlap shall increase proportional to the increase in height such that the ratio of overlap to clear opening height is equal to or greater than the ratio in the successfully tested specimen.

7. Clause 4.3.4 The following types of fire barriers systems shall additionally conform to ISO 21524:2021

Comments:

Pass doors in active fire curtains are unnecessary and can pose more danger than safety. Emergency Retract Buttons (ERBs) are a safer and simpler solution to escaping through a fire curtain when safe to do so. Some pass doors in active fire curtains have a trip hazard threshold (bottom bar). Another potential issue are the problems posed to an untrained end user struggling with the fastening (and knowing what to do) in a fire situation. The biggest danger of pass doors is there is no way to stop someone from opening a pass door if there is a fire on the other side which could be very dangerous or even fatal to the user and endanger the whole building. This could be compounded if, due to the fire, the pass door was obstructed from resealing.

It is safer and simpler to use an ERB (Emergency Retract Button) to allow safe egress and escape beyond a fire curtain that has already deployed. ERBs will retract the curtain for a preset time before redeploying – but they only work if it is safe to do so when used in conjunction with thermal and smoke sensors. An ERB can be (and should be) micro-switched to thermal and smoke sensors that prevent activation if either smoke or fire is present on the other side (the blind side) of the curtain, thus providing a safe and controlled means of exiting in that direction if it is safe to do so. ERBs are simpler for the end-user, and safer for everyone.

Proposed changes:

Prohibit the use of pass doors in all active fire curtains and safely control (and prevent if necessary) the opening of fire curtains after they have deployed by using thermal and smoke sensors on the blind side of the fire curtain that are micro-switched to the ERB (open) switch.

8. ISO 21524 and pass doors

Comments:

When ISO 21524 is revised we would suggest pass doors are prohibited for the same reasons pass doors should have been prohibited in BS 8524-1. Fire safety has to come first. If something is potentially dangerous, even if it is potentially helpful, if the potential danger cannot be controlled to an acceptable level then another way of achieving the potential value should be found (if it doesn’t already exist)

Proposed changes:

When ISO 21524 is revised we would suggest pass doors are prohibited for the same reasons pass doors should have been prohibited in BS 8524-1.

9. Clause 4.3.4 The following types of fire barriers systems shall additionally conform to ISO 21524:2021

Comments:

Vision panels in fire curtains are a gimmick with close to zero value and including them in the standard risks implying value which may subsequently be used to lead (or on its own may lead) specifiers and buyers to believe they are providing a higher level of safety to their clients by including them when in reality they will be paying for nothing of value. A British standard should lead to and encourage best practices for the safety. Paying for a gimmick is not best practice.

Current designs of vision panel are manufactured from a combination of silicone on a silica fabric glass substrate. This clouds up at circa 300°C which is only seconds into a fire using the heat curve in BS EN 1363 which shows the temperature after 5 minutes is 576°C (Fig. 5). This means any vision panels is opaque before any emergency services could reach it and it be of any value – even if they were going to rely on a small square of visibility to make decisions about entering a room or not.

Commercially driven pressure from private entities that may have invested in these vision panels should not have been considered a valid driving force to include them in BS 8524 and ISO 21524 and any other fire curtain related standards.

If a manufacturer wants to convince a paying customer of the value of vision panels, let them try, but standards should not be used to assist that. Standards should specifically avoid including gimmicks for at least two reasons:

a. to avoid gimmicks being enshrined and implying they have value, and,
b. to keep the standards as concise and simple as possible for the consumer so they can be followed as easily as possible.

Anything that does not help improve fire safety for the consumer should be removed from the standard, rather than including ‘in case’. There is enough expertise available to ascertain the benefit of something so as to avoid the latter.

Even if the vision panels on the market actually worked for a meaningful time, they would be of negligible value in a fire when rooms are filled with smoke. Thermal and smoke sensors are significantly better to advise the fire services as to the presence of smoke and/or fire in a room – and readings from such sensors can be fed back to a central point, even off-site if needed.

Even if vision panels remained transparent for a meaningful time, it would be highly unlikely fire services would be content with using a small vision panel to comprehensively check a room for the presence of people. If it is safe to enter then the ERB (Emergency Retract Button) should be used to enable a thorough check before resealing the room.

All of these points are without considering the impact on the integrity of the fire curtain by cutting a hole in it and introducing a seamed joint that can come apart over time.

Proposed changes:

Remove all reference to vision panels from the standard BS 8524 (and from ISO 21524 when it is revised). Even better would be to add some text explaining that they are a gimmick and do not work in a fire and merely introduce a weakness to the fabric curtain as well as being a potential major intervention maintenance requirement.

10. Table 3 (under 5.6) – Fire resistance test standards for barrier assemblies

Comments:

References to BS 476 should be removed. We have known for 20 years that it is inferior to its European counterparts and have held on to it to protect UK manufacturers. This just means UK manufacturers who have kept using it have fallen behind their European counterparts and safety standards in this country lag other leading and developed countries.

It does not help credibility for UK manufacturing or UK exporting. You can view a short video on the Adexon Fire & Smoke Curtains website explaining this in brief, Why scrapping BS 476 I good for safety2.

Proposed changes:

Remove all references to BS 476 in BS 8524

11. Clause 5.5 Smoke containment

Comments:

Cold smoke seals should not be permitted as a means of smoke control unless they are used in conjunction with intumescent strips like they are on fire doors.

Cold smoke seals do not provide smoke protection at elevated (fire) temperatures.

Using the heat curve in BS EN 1363 (Fig. 4), the temperature after 5 minutes in a fire is 576°C. Cold smoke seals are made from polypropylene filament which melts at circa 170°C meaning they melt after a few seconds when exposed to a fire.

Another serious risk they pose to the life-safety critical performance of the active fire curtain in the event of a fire is if they become detached and thus, loose in the side-guide, they block the fire curtain fabric from travelling down the guide and deploying to the fire-safe position. This is not an uncommon issue.

Destructive access is often the only way to resolve this issue of detached smoke seals, so it is a lengthy and costly maintenance issue to resolve. See this case in point3. This is a site in central London that has given up on the supplier of these BS 8524 fire curtains and is replacing them all after only 4 years, at a multiple six figure cost.

Another potentially even more dangerous risk with cold smoke seals is that they spontaneously combust at circa 200°C (still only seconds into a fire using the BS EN 1363 heat curve shown in Fig. 4). The risk here is that cold smoke seals on active fire curtains are fitted on both the fire side and the non-fire side in such close proximity to the curtain that no amount of insulation value would prevent them from spontaneously combusting and thus spreading flame onto the non-fire side only seconds into a fire. This is a risk that cannot be ignored.

Whilst advocates of cold smoke seals may point to the fact that they pass the cold smoke test, BS EN 1634-3, there are a number of points that vindicate prohibiting the use of cold smoke seals etc on active fire curtains:

a. BS EN 1634-3 is deficient as it does not reflect real life fires. There is an opportunity to rectify this with it currently being revised. It would be an error for BS 8524 to lean on a deficiency in another standard to compound the non-performance of cold smoke seals when used on their own in real life fire scenarios.
b. Cold smoke seals spontaneously combust on the non-fire side after only seconds into a fire.
c. Cold smoke seals are prone to becoming detached within the side guide and hence block the travel of the fire curtain and prevent deployment. This issue also creates the need for major maintenance interventions at great expense and disruption to the customers whilst also meaning the fire safety of the building is defective while the remedial works are scheduled and carried out. This could be 10 weeks or more if new fire curtains need to be manufactured. The building/s should be closed during this period.
d. Cold smoke seals were never intended for use on active fire curtains. They were designed for use on fire doors where they are used in conjunction with intumescent strips. The cold smoke seal provides smoke sealing up to temperatures of circa 170°C, and the intumescent strips ‘activate’ at circa 180° Together they give essentially contiguous smoke protection. Further, there is no issue with them falling off on a fire door – access is not destructive (simply replace), and they don’t block or hinder the operation of the fire door should they become detached. They are also visible so if they do become detached it is not likely to remain unknown until too late (on a fire curtain they are out of sight).
e. On a fire curtain, you cannot use intumescent strips, so the cold smoke seals are on their own. When they are gone, they are gone, and there is no smoke protection.
f. Whilst a hot smoke test isn’t available (yet – we are advocates of it), you can still have smoke seals that are manufactured from fire-resistant components. You can also have smoke seals that do not cause a flaming issue on the non-fire side.

You can read about modern improved methods of smoke sealing on active fire curtains on the Adexon Fire & Smoke Curtains website, The science behind cold smoke seals4 and Are cold smoke seals in fire curtains a cause for concern?5

Other forms of smoke seal that have been used for fire curtains tested to BS 8524-1:2013 include rubber draft excluders and these pose the same issues as cold smoke seals as above.

None of these attributes or issues are best practice. Standards are proponents of best practice.

Proposed changes:

Prohibit the use of cold smoke seals and rubber draft excluders on active fire curtains. Prohibit the use of flammable materials on active fire curtains. Prohibit the use of components in the side guides that could potentially become detached and thus block the fire curtain fabric from travelling and deploying to the fire safe position. Mandate the use of newer designs of smoke sealing that are available for manufacturers to follow (not patented).

12. Clause 5.8.7 Where pressure-sensitive protective equipment is provided, such as a safety edge, it shall conform to BS EN 12453:2001, 5.1.1.6, and shall stop deployment of the barrier assembly on operation

Proposed changes:

Has anyone ever used a safety edge on a fire curtain? Does anyone advocate their use? If not, remove any reference to them from the standard.

13. Table A.1 – Test order

Comments:

In the absence (as yet) of the requirement in BS EN 1634-3 for a hot smoke test, the order of testing should replicate as closely as possible real-life conditions so as to assure the consumer of fitness for purpose of the product. This means carrying out the fire test before the smoke test.

Proposed changes:

Stipulate that the smoke test is carried out on the same specimen as the fire test, after the fire test has been done, and provide a smoke rating in terms of how long it is able to provide smoke sealing to the required levels at fire temperatures. This tells the consumer (and the fire engineer designing the strategy) that the product is going to prevent the passage of hot smoke and gases for X minutes.

14. Annex C General requirements for testing

Comments:

Requirements for testing should extend to what information is available to the public. Information available to the public should at least include:

a. Product dimensions tested successfully and what ratings were achieved (E, EW, EI including minutes).
b. The fixings used in the successful tests and what substrates the product was fixed to.
c. List of material specifications and components of the successfully tested products.
d. Critical dimensions of products/ components e.g., relative to each other.
e. The orientation tested (if only one side is tested).

This information enables the consumer to check they are getting the same product as was successfully tested (critical) and removes the temptation for manufactures to substitute components (e.g. if a tested component is on an unexpectedly long lead time, or another untested component “will do the same job” and/ or is available cheaper etc) or moving how components sit relative to each other because it is difficult to mass produce in the tested configuration/ position and “it won’t make any difference” in the eyes of the manufacturer (and no one will ever know).

Proposed changes:

Mandate that information is available to the public at least including:

a. Product dimensions tested successfully and what ratings were achieved (E, EW, EI including minutes).
b. The fixings used in the successful tests and what substrates the product was fixed to.
c. List of material specifications and components of the successfully tested products.
d. Critical dimensions of products/ components e.g. relative to each other.
e. The orientation tested (if only one side is tested).

This information enables the consumer to check they are getting the same product as was successfully tested (critical).

15. Annex G Test method for reliability of motor operation at elevated temperatures

Comments:

BS 8524-1:2013 requires fire curtains to conduct a hot motor test, where the motor must operate 12 times over 30 minutes with the furnace temperature at 400°C ± 20°C. This is dangerous for the following reasons.

Hot water burns us at around 70°C. It scalds us at 100°C. The emergency services would not open a fire curtain with the temperature at even half of 400°C as it would exceed the limits to which firefighters are trained; see “Characterizing a Firefighter’s Immediate Thermal Environment in Live-Fire Training Scenarios”6 which states “severe training conditions generally [exposed firefighters to] temperatures between 150°C and 200°C”
A fire curtain should never be operable if there are temperatures of 400°C on one side, as this would pose a severe-to-fatal risk to the operator and could allow the fire to pass beyond the designated compartmentation line and thus endanger the whole building.

It could be argued that the hot motor test is for applications where the motor is high above the operator, for example in a ceiling void. In this situation, if there were a fire in the void and not lower down, and if you wanted to operate the fire curtain, you have a rare combination where a hot motor use may be applicable. But what is the incidence rate of this combination, and who is going to stop the curtain from opening above the safe temperature limit so as to prevent the fire from spreading? If it is 400°C up where the motor is, and 20°C down where the operator is, it stands to reason there is a temperature gradient in-between.

What is the safe height to open the curtain to? Who is going to know this, let alone do it when escaping from a fire?

To justify this test being of potential value, data is required to show how often this combination occurs, and a control measure is required including easy-to-use instructions by the user in a fire situation, so they don’t open the fire curtain too far and thus endanger themselves or the building further. A failsafe back up to stop the fire from spreading is also required in the event of user error. Otherwise, this is a dangerous capability, and the motors should be designed so they do not work at elevated temperatures.

The capability for an untrained person to operate the motor at 400° in the vast majority of circumstances is dangerous. Whilst this test may have the best of intentions, on the balance of risk that it poses in its current format versus any benefit it may provide in very rare circumstances, it should be removed.

Note. Even if this test were a good thing and if it could have benefits somewhere, the expansion of the bottom bar at 400°C is untested and it is very questionable whether the motor would be capable of moving the curtain if the bottom bar had expanded and jammed in the guides.

Proposed changes:

Remove the ‘hot motor test’ and stipulate that the motors on active fire curtains should be designed so they do not work at elevated temperatures for the reasons stated above.

This white paper was written by the team at Adexon Fire & Smoke in October 2023. It includes the views of the Adexon team and its intention is to raise awareness and standards in the fire curtain 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.

We have a free RIBA CPD on active fire and smoke curtains, either in-person or online, you can book online7 (or contact us).

And/ or keep up to date on regulations and standards around fire curtains with our ‘Fire Safety Insights monthly newsletter8.

16. Additional reading

For an example of going above and beyond legal compliance, read, ‘Are cold smoke seals in fire curtains a cause for concern?’5

If you are interested in impact testing, read why the design of the fabric retention and the durability of fire curtain designs is paramount, ‘Active fire curtain maintenance- and the 3 reasons fabric retention design matters’1

If you would like a deep dive read on the regulations applicable to fire curtains, you can find this in our white paper ‘Fire curtain regulations in the UK’9

17. References

1 Adexon Team (2023) Active fire curtain maintenance – and the 3 reasons fabric retention design matters, Adexon. Available at: https://www.adexon-uk.com/article/why-fabric-retention-design-on-fire-smoke-curtains-matters-a-lot/

2 Adexon Team (2023) Why scrapping BS476 is good for safety, Adexon. Available at: https://www.adexon-uk.com/video/why-scrapping-bs476-is-good-for-safety/.

3 Bigwood, T. (2023) Tom Bigwood on linkedin, Tom Bigwood on LinkedIn: #firesafety #firecurtains #smokecontrol. Available at: https://bit.ly/gsfcsurvey (Accessed: 29 August 2023).

4 Adexon Team (2023d) The science behind cold smoke seals, Adexon. Available at: https://www.adexon-uk.com/science-behind-cold-smoke-seals/ (Accessed: 29 August 2023).

5 Adexon Team (2023) Are cold smoke seals in fire curtains a cause for concern? , Adexon. Available at: https://www.adexon-uk.com/cold-smoke-seals-in-a-fire/ (Accessed: 30 June 2023).

6 Willi, J.M., Horn, G.P. and Madrzykowski, D. (2016) Characterizing a firefighter’s immediate thermal environment in live-fire training scenarios – fire technology, SpringerLink. Available at: https://link.springer.com/article/10.1007/s10694-015-0555-1.

7Adexon Team (2023) RIBA accredited CPD course, LinkedIn. Available at: https://lnkd.in/e8RrY3Q6 (Accessed: 09 November 2023).

8Adexon Team (2023) Fire safety insights, Adexon Newsletter. Available at: https://bit.ly/AdexonNews (Accessed: 09 November 2023).

9 Adexon Team (2023) Fire curtain regulations in the UK, Adexon Resources. Available at: https://www.adexon-uk.com/whitepaper/fire-curtain-regulations-in-uk/.