Safety is the standard – a detailed look at BS 8524 and why it can no longer be used for fire curtains.

2. Product standards

Product standards play a key role in ensuring that products of all types meet particular performance, quality, and safety standards. They are developed over many years by industry representatives who come together to agree on the appropriate requirements and testing procedures. This enables purchasers to understand what to expect from a product since it meets the requirements of a specific standard.

Product standards are made up of a series of complimenting product tests to form an ‘as-close-as-possible’ holistic assessment of the product in a real-life application. This is a big improvement from just testing a product to a single product test such as a fire test.

BS 8524 and BS EN 16034 are both examples of product standards that cover fire curtains, both comprising the following product tests: a fire test, a smoke test, and a cycle test, amongst other requirements.

Whilst standards can be very important and can make a significant contribution to consumer safety, regulations take precedence over them. As BSi tells us, “Compliance with a British Standard cannot confer immunity from legal obligations” and “standards aren’t the same as regulations and following a standard doesn’t guarantee that you’re within the relevant laws. In fact, standards rarely cite the law as legislation could change within the lifetime of the standard”.

If you are interested in reading more around regulations that apply to fire curtains, we have a comprehensive white paper on the subject, Fire curtain regulations in the UK¹

Product standards for active fire curtains are no different to others – they set out performance requirements and put the products through a series of tests, enabling them to prove their performance. There are three main product standards that have been used over the last decade for active fire curtains in the UK:

• British standard BS 8524: 2013 Active fire curtain assemblies, Parts 1 and 2;
• International standard ISO 21524:2021: Requirements for active fire curtains; and
• European harmonised standard BS EN 16034: 2014 Pedestrian doorsets, industrial, commercial, garage doors and openable windows – Product standard, performance characteristics – Fire resisting and/or smoke control characteristics. 

3. BS 8524

When the British Standard BS 8524 was published in 2013 it superseded the former fire-curtain specification, PAS 121:2007. Whilst it was a welcome improvement at the time there were still a number of deficiencies resulting in poor products being able to achieve BS 8524 and get to market. A recent survey at a £1bn office development in central London for a large global bank is a case-in-point³.

These deficiencies likely contributed to its demise, but it was really the European standard BS EN 16034 becoming harmonised on 1st November 2019 that signalled the end of BS 8524 for the foreseeable future, at least for vertical fire curtains.

The withdrawal of support for BS 8524 culminated in Warringtonfire and then IFCC pulling out from offering third-party certification for the standard. This resulted in the last valid third-party certification for BS 8524-1 expiring on 9th June 2023 meaning BS 8524 fire curtains should no longer be sold or purchased after that date.

In the future a new revised version of BS 8524 may be published, and this may regain Notified Body support but there is an indefinite and lengthy timeline. And these ‘maybes’ are presuming it can be justified that BS 8524 is not a ‘conflicting national standard’ with regards to BS EN 16034. If BS 8524 doesn’t overcome this ‘conflicting standard’ hurdle it will have to be formally withdrawn.

Thankfully the harmonised European standard BS EN 16034 that is legally required for vertical fire curtains is a comprehensive and current product standard that is fully supported with valid third-party certification from Notified Bodies. These certification schemes are accredited by the likes of UKAS.

This white paper is not advocating the use of BS 8524 by virtue of reviewing it. We believe BS 8524 should be formally withdrawn as it is a national standard that conflicts with BS EN 16034 for vertical fire curtains. You can read more about the work we have done on a revision of BS 8524 should it not be formally withdrawn in our article, BS 8524-1: A conflicting national standard that should be formally withdrawn – and the improvements it needed²¹.

4. Two Parts of BS 8524

BS 8524 consists of two separate parts.

BS 8524-1: 2013 Active fire curtain assemblies – Specification, is related to the product itself and outlines requirements for the design, testing and classification of the fire curtains. It brings together a number of complimenting tests (and some not-so-complimentary tests). We have submitted to BSI that if BS 8524 is to have a future version, some of the less desirable and arguably dangerous tests should be removed.

BS 8524-2: Active fire curtain barrier assemblies. Code of practice for application, installation and maintenance, recognises that the maintenance of fire curtains throughout their lifetime is important. It is a code of practice and it is misleading to say, “BS 8524 Part 2 has third-party approval” implying it is a unique benefit of BS 8524. There is a third-party approval scheme for the installation of fire curtains run by the IFCC called SDI 05 ‘Fire And Smoke Curtains (Active Or Passive)’. This is available for fire and smoke curtain products certified to the standards BS EN 16034, BS 8524-1 (when it had valid certification), and ISO 21524.

A significant element of Part 2 is the same text on regular checks that you will find in the manufacturer’s Operation & Maintenance manual to help comply with the Regulatory Reform (Fire Safety) Order 2005 (the ‘FSO 2005’). These include what should be done regularly on site, and those actions that are less frequent and must be undertaken by a competent engineer.

An example is the advice to check for obstructions that might prevent the curtain from deploying, such as alterations to cosmetic finishes, lighting, shelving or racking, furniture or temporary displays. However, the most common obstructions we find preventing deployment are within the design used for BS 8524 fire curtains themselves. The older designs used on BS 8524 fire curtains use a smoke seal or rubber draft excluder to provide smoke control. These are prone to becoming detached and blocking the side guide. See this case-in-point³.

5. Third-party approval of installation and the FSO 2005

The SDI 05 installation scheme offers specifiers and fire authorities a degree of confidence that the product’s installation as a life-safety device is competently carried out. There are specified requirements for installation although these are not comprehensive and the most reliable method for ascertaining correct installation remains the actual testing of the product at the point of commissioning, and then each week, in the same manner as it would be required in a fire.

A legal requirement of the Regulatory Reform (Fire Safety) Order 2005 (the ‘FSO 2005’) is that life-safety products such as fire curtains “are subject to a suitable system of maintenance and are maintained in an efficient state, in efficient working order and in good repair”. Essentially, if it works each week on the tests and this is recorded, this is more reliable evidence of ‘working order and good repair’ than historic installation paperwork.

We have encountered end-users not carrying out weekly testing of their fire curtains due to recurring jamming issues they are experiencing. This can be traced back to certain designs of older fire curtains4. Regardless of installation paperwork, if the product doesn’t work when tested it isn’t fit-for-purpose in its current state and needs urgently looking at by a specialist. If not, the Responsible Person risks breaching the legal requirements of the FSO 2005 and this is critically more important than any code of practice, however well-intentioned.

It is also important to note that the SDI 05 installer scheme does not check the manufacture of the product so should only be used as the ‘icing on the cake’ for fire curtains that already have valid third-party product certification. If the product supplied is potentially different to the test specimen, it matters not how well installed it is. Valid third-party product certification is your ‘insurance policy’ that the product supplied is the same as the test specimen.

Whilst the SDI 05 scheme recommends the fire curtain should be operated at least monthly, and on escape routes weekly, Adexon advocates all fire curtains are tested weekly along with other life-safety equipment such as the fire alarm. Where the fire curtain forms part of a smoke control system protecting a means of escape, it should be tested in conjunction with the smoke control system.

These weekly tests, as outlined in the manufacturer’s Operation & Maintenance manual, include the self-closing devices, automatic release mechanisms via a test switch, the sensory detection equipment, and self-test facility.

The take-away here is that third-party approval of the code of practice for installation is fine to have so long as it doesn’t create a false sense of security or complacency that the paperwork is a substitute for a reliably working fire curtain.

6. The tests and annexes within the standards

Like the other standards, BS 8524 tests the product for fire resistance and other aspects of the parts that make up the finished assembly. This includes the fabric curtain, motor drive, frame, electrical power and control systems and associated ancillary devices. It requires a series of operational tests to be undertaken prior to testing on the furnace. These ensure the components all work independently of each other. To read about these in more detail and to see a full technical comparison of BS 8524 with BS EN 16034, read the Adexon white paper, A technical comparison of BS EN 16034 and BS 8524².

BS 8524 includes annexes of mixed value. These are:

Annex A (normative) Overlapping multiple barriers.
This explains that the values for the minimum width of the end curtain and the minimum width of the overlap are calculated based on values recorded during the fire test. We believe it is important for the consumer to be able to check the amount of overlap tested and that this is related to the height (drop) of the fire curtain. It is obvious that a higher curtain would require more overlap. For example, 1m of overlap may suffice for a 2.2mH fire curtain but it is highly unlikely it would suffice on a 10mH fire curtain. This critical information is not available under BS 8524.

Annex B (normative) Order of testing.
This defines the order of testing for each specimen.

Annex C (normative) General requirements for testing.
This includes dimensions, fixing methods, joints, and seams etc. Unfortunately, little to none of this information is displayed in the publicly available BS 8524 documentation leaving it to the manufacturers to disclose what they feel best. Conversely, in the BS EN 16034 third-party certification from Applus, the end-user is provided with a mandatory ‘Technical Annexe’ covering extensive details that are critically important to the performance of the product.

Annex D (normative) Test method for barrier assembly reliability and response time and the durability of materials
Whilst this annex states that the barrier assembly must be tested for its reliability and response time using the control system with which it is intended to be used, there are no publicly available details of what was tested meaning you could get something different to what was tested.

This was one of the critical shortcomings of BS 8524 and its paperwork and was compounded by BS 8524 losing Notified Body support on 9th June 2023 meaning there is now also no valid third-party certification available for it. You can read more about how important this is for risk in the Adexon article, How valid third-party certification reduces your risk⁶.

The annexe also requires the specimen to be tested in the orientation intended for use by the manufacturer. The downside to this is that there is no publicly available documentation to tell the consumer (or even the installers) what this orientation is meaning it could be installed the wrong way around, sitting with its untested side to the fire which could have fatal consequences.

The reliability and durability testing simulates the usage of the curtain, with the required 500 cycles representing one test each week for 10 years. This cycle test is required in all three of the abovementioned standards, but the aspiration to cycle test before the fire test shows the fabric still provides a fire barrier after years of use. The caveats/ limitations to the benefit of this are:

1. 1. the same curtain fabric being used for both tests, including the full and same size e.g. only part of the curtain fabric that was cycle tested may be used in the fire test.
   2. installation in ‘real-life’ being as good as and the same as the tests.
   3. not testing the areas of the curtain where the most common cause of wear, tear and ripping in curtains happens i.e. around the retention bolts/ poppers (where still used). It renders the ‘cycle test before fire test’ of negligible value if the fabric tearing issues the old designs are susceptible to are not fire tested. Watch the following short video to see the difference between the old designs and the newer designs. The newer designs are tested to BS EN 16034 and ISO 21524⁴.

Similar to BS EN 1192, Annex D requires the barrier assembly to be tested for impact. This simulates a body colliding or falling into the closed curtain, which is important when the curtain is used along an escape route. A 50kg soft weight is dropped against the face of the curtain (at two different heights) with an impact energy of 100Nm prior to cycling the curtain for 500 operations. At the end of cycling, the curtain is subjected to the impact test again and the curtain is checked for damage. Whilst this seems a helpful test in theory, when we see what still happens to curtains that have passed this test it raises questions as to the effectiveness of the testing criteria. You can read more about what happens and why in our article, The quiet transformation happening in the fire curtain industry²².

Annex E (normative) Test method for motors
The motor reliability and durability testing has little safety benefit as fire curtains tested to any of the abovementioned standards have to deploy under gravity (without the motor working). The motor is tested to lift a weight equating to 90% of the maximum load, over a distance of 3m before it is released. There is a universal classification given to the number of cycles attained: C1 for 500 cycles, C2 for 10,000 cycles, C3 for 50,000 cycles.

Annex F (normative) Calculation of ambient temperature smoke leakage.
For more in-depth information about smoke testing, read ‘The science behind cold smoke seals’<sup8 and ‘Are cold smoke seals in a fire a cause for concern?’⁹.

Annex G (normative) Test method for the reliability of motor operation at elevated temperatures. 
This test is carried out by placing a motor specimen in a furnace and operating it at maximum load following a prescribed timeline heat curve for a specified number of cycles. Elevated temperature testing of motors provides evidence that the motor will continue to function during the start of a fire, allowing the fire curtain to be retracted to release anyone trapped or for the Fire and Rescue Service to pass under the curtain. In theory, this could be seen as a good test, as it potentially shows the robustness of the curtain’s control mechanism, even under extreme conditions.

However, in practice, the Control Panel that operates the motor would melt and/ or cease to function long before a temperature that threatens a motor is reached, and a fire curtain should never be operable if there are temperatures of anything approaching the upper limit tested 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 barrier and thus endanger the whole building. You can read more about this in the technical comparison white paper already referred to, and the Adexon article, The dangers of the hot motor test in BS 8524-1¹⁸

Annex H (normative) Test method for ancillary and optional equipment

Annex I (informative) Typical product performance summary

The annexes and test methods are intended to show the performance of the product in use. However, without valid third-party certification for BS 8524 there is no longer any independent inspection and auditing by a Notified Body to ensure the product reaching site is the same as the tested specimen.

7. Will BS 8524 achieve valid third-party certification again?

No one could provide indemnify against a date when third-party certification will be available again for BS 8524 due to the uncertain future it faces and the indefinite and lengthy process before valid third-party certification for BS 8524 could be available again. The high level view of the process is:

• BS 8524 needs revising
• Notified Bodies then need to create a scheme that can be assessed and accredited e.g. by UKAS
• Manufacturers then need to pass the new tests in BS 8524 including the European standards fire test
• Then certification, audits, paperwork, and Factory Production Control needs to be completed

If BS 8524 achieved third-party certification again it will still be a legal requirement to CE mark all vertical fire curtains to BS EN 16034. The foreword of the harmonised standard, BS EN 16034, states, This European Standard[BS EN 16034] shall be given the status of a national standard… and conflicting national standards shall be withdrawn at the latest by October 2019”. This won’t change until BS EN 16034 changes, the CPR changes, or BS 8524 becomes harmonised. None of these are likely within the next five years, if ever (BS 8524 is highly unlikely to ever become harmonised).

8. A future for BS 8524-1?

BS 8524 was a good start to a dedicated product standard for fire curtains when it was published in 2013. The international standard ISO 21524 builds on the good within BS 8524, providing long term scope for a dedicated fire curtain product standard without the weaknesses seen in BS 8524. There is still a lot of work to be done with ISO 21524 as several of the deficiencies of BS 8524 have been incorporated to date. Adexon are now on the BSI National Committee that contributes to ISO 21524 so will be working with the rest of the committee to make these improvements on the next publication.

The big question with regards to BS 8524 is that it remains to be seen if it has a future. Key factors are that it is neither harmonised nor internationally recognised. The market in the UK is relatively small, fire curtains are a niche product, and it is a question as to whether it is financially viable for Notified Bodies to run certification schemes for a ‘nice-to-have’ standard such as BS 8524 that can only be used in a comparatively small geographical market when they can run schemes for BS EN 16034 (a harmonised standard legally required⁵ under the CPR and with European wide appeal) and/or ISO 21524 which has international reach. It would seem that IFCC and Warringtonfire concluded BS 8524 was not viable to continue supporting, with or without its deficiencies, otherwise it would stand to reason they would have resourced themselves accordingly and stood with it whilst it underwent revision.

Without valid third-party certification from a Notified Body, BS 8524 loses its main benefit of independent inspections and audits that ensure the products reaching site, and the components, are the same as those that were tested originally.

In conclusion, even ignoring the requirement for BS 8524 to be formally withdrawn as being a conflicting national standard to BS EN 16034, the odds are stacked against BS 8524 coming back even from commercial and common sense perspectives, having no regulatory mandate, a better and newer competitor that appeals to all the international markets (ISO 21524), and for the foreseeable future the harmonised standard BS EN 16034 being legally required for all vertical fire curtains (circa 90% of the total fire curtain market).

9. ISO 21524 fire curtain standard

As already mentioned, ISO 21524 is an international standard for fire curtains that some say is the long-term future for all configurations of fire curtains. However, like BS 8524, it is not harmonised so cannot be used for vertical fire curtains in the UK or EU markets.

ISO 21524 also has no third-party certification scheme for concertina fire curtains meaning it is currently limited to horizontal fire curtains. It could be used for concertina fire curtains if a Notified Body creates a certification scheme for them. Concertina fire curtains currently have third-party certification schemes available to BS EN 16034 and, due to the size of the market and the financial viability of competing schemes with very little demand, it would seem there is no appetite from Notified Bodies to create an ISO 21524 third-party certification scheme for concertina fire curtains.

Improvements required to ISO 21524 include removing features of questionable value and safety such as pass doors and vision panels. Neither feature makes sense practically or for safety. You can read a detailed appraisal of these in our article, BS 8524-1: A conflicting national standard that should be formally withdrawn – and the improvements it needed²¹, as these features originated from BS 8524. Below we include a brief overview.

Pass doors in fire curtains have a number of issues ranging from the trip hazard threshold (bottom bar) to the panic-accentuated user problem that occurs trying to undo the Velcro in a fire escape situation; it is much simpler and safer to use an ERB (emergency retract button). ERBs will retract the curtain for a preset time – if it is safe to do so. This latter point is very important as there is no way to stop someone from opening a Velcro 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. Conversely, an ERB can be micro-switched to thermal and smoke sensors that prevent activation if either is present on the other side of the curtain.

Reference to vision panels should be removed altogether in the standards. 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 (refer to the heat curve in BS EN 1363, Fig. 1 which shows the temperature is 576°C after only 5 minutes). This means vision panels are opaque before emergency services reach them – even if they were going to rely on a small square of visibility to make decisions about entering a room or not.

Even if vision panels remained transparent for any length of time, they are of negligible value when rooms are filled with smoke. Thermal and smoke sensors can advise the fire services centrally as to the presence of smoke and/or fire, and it is negligent to recommend that a room-sweep check for people needing to escape is done courtesy of a small grainy window in the fire curtain. If it is safe to enter then the ERB should be used to enable a thorough check before resealing the room.