Reading and understanding British Standards and Codes of Practice is the fire safety specialist’s bread and butter, but sometimes there are pitfalls that it can be easy to fall into. The Fire Industry Association has recently produced guidance about BS 7273-4:2015 and its application. This particular British Standard can be difficult to follow without some careful consideration. It’s important to understand all the technical ‘ins and outs’. On that basis, Robert Thilthorpe assesses the fine detail.
BS 7273-4 Code of Practice for the Operation of Fire Protection Measures – Part 4: Actuation of Release Mechanisms for Doors was published on 30 June 2015. It replaces the 2007 version, which is superseded. Although the 2015 version is now three years old, it’s all-too-easy to forget which parts were updated.
In a nutshell, BS 7273-4:2015 is concerned with the operation and release of electronically-controlled fire doors. It recommends how to actuate mechanisms that unlock, release or open doors in the event of fire in all types of buildings including dwellings (except where stated).
The British Standard provides recommendations for the design, installation, commissioning and maintenance of electrical control arrangements for the actuation of mechanisms that unlock, release or open doors in the event of fire. The document’s contents apply to all aspects of the interface between these mechanisms and a fire detection and fire alarm system, including interfaces that incorporate acoustic coupling and radio transmission.
The document also enhances some of the recommendations of BS 5839-1 with regard to detector siting and spacing in certain categories of system. Don’t be caught out here: both British Standards should be referred to when specifying systems.
Door release mechanisms
Why might electronically-controlled doors be used anyway? There are a number of instances where electronic door release mechanisms might be used. For those that are already resident within the security world, these may be obvious and apparent since security itself is one of the main reasons it might be considered.
For security reasons, it might be necessary to keep a particular door shut, but it may be impractical to keep it locked with lock and key, since if the door is also being used as a fire exit, people will need to use it to escape. In this case, controlled-access doors with an electronic door mechanism may be installed if there’s a need to release the door in case of fire (for example, if the door leads to staff areas).
The second reason why a door release mechanism may be used is down to accessibility. In some situations, for the sake of accessibility, there may be a need to keep doors in corridors open. However, as we all should be aware, an open door invites fire to spread much more rapidly through a building. Here, a door mechanism may be employed to close doors and prevent the spread of fire.
The final reason for installing a door release mechanism is simple: convenience. In some situations, such as doors to shops, it may make more sense to install automatic doors that will open in the event of a fire episode to ensure the safe exit of all staff, customers and any site visitors.
From these three examples, it’s easy to see how different doors for different buildings can be used in different ways. In some circumstances there are also different needs, too. That all depends on whether the door needs to open or shut in the event of an outbreak of fire.
Problems with BS 7273-4
As such, the problem with the application of BS 7273-4 is that it can be a very demanding standard that may be difficult to meet due to the different needs and requirements of different doors throughout the building.
Which doors should be released and when? How do you make the fire alarm system communicate with the door release mechanism? How do you ensure that the ‘fail-safe’ works? The situation can sometimes be made all the more complicated in bigger buildings housing multiple storeys and a wide variety of doors.
In addition, different buildings have different needs. Each case needs to be treated individually. What might work for one building might not work for another, even if there are many similarities (as we’ve already seen).
There’s also a conflict between two British Standards here. What BS 5839-1 says may confuse your interpretation of BS 7273-4. If you’re wondering, by the way, the answer is that BS 7273-4 takes precedence (but only for category L4 or L5 systems). If the design of the building calls for a category L1, L2 or L3 design, stick with BS 5839-1 and the guidance within. Otherwise, for category L4 or L5 systems, design the system with BS 7273-4 in mind. That said, this comment piece is by no means a substitute for reading the British Standards and obtaining the relevant training.
Working with BS 7273-4
Tip #1: Identify the type of door mechanism. Is it going to unlock or just open? How will you make sure the door fulfils its role as a fire door?
Door release mechanisms are typically one of three things. They could be electromagnetic door holders that release self-closing doors in an emergency or electromagnetic locks that prevent unauthorised access, but will still release in an emergency. They could be powered sliding doors that open in an emergency. Take this into consideration when thinking about fire doors and their purposes.
Tip #2: Identify the categories of the door systems. By identifying the category of door system, you can then base your design for the alarm system on these factors.
For those of you not ‘in the know’, there are three categories that you need to worry about: critical, standard and indirect. Where and how you can use these different categories of door system depends a great deal on the building and the environment in which you’re working. In some cases, it may be worth noting that enforcing authorities may not allow electronically-secured doors, such as in school buildings where only the critical category of doors may be applied if and when permitted.
There are further areas of guidance that may need to be considered if the building is a hospital, a care home or an HMO.
Tip #3: If you want to know what type or category of fire door you’re working with, Annex B in the British Standard is your friend. Annex B of BS 7273-4 details the different categories of fire door and helps you clarify what you’re working with.
If you don’t have a copy of BS 7273-4, you can purchase one from the British Standards Institution’s website. Alternatively, if you decide that you would like your company to become a member of the Fire Industry Association, you can obtain British Standards at a specially discounted rate (which is just one of many handy perks of FIA membership, in fact).
In addition, the FIA has published a technical document that will help break down BS 7273-4. ‘FIA Application Guidance on BS 7273-4:2015’ summarises the standard and should work as an aide memoir. In this document you’ll learn more about door release mechanisms, etc.
Robert Thilthorpe is Technical Manager at the Fire Industry Association