Detection around magnetic hold open devices

[Taiter]

Can anyone tell me if there is a requirement to have a detector head either side of a fire door that is fitted with a magnetic hold open device in a corridor.  I'm sure I read that there was, but can't find it anywhere.  Any info very welcome.  Thanks

[kurnal]

This used to be a common requirement in the early days of these things (was it 3 m or 1.5 I cant remember)  but If I recall it dissapeared in 1988 with the issue of  BS5839 part 1 as types (now categories) of system were defined.

Nowadays theres nothing to stop such an arrangement being provided under an L5 system!

Remember  also that where you ask for an L3 system if a large open plan area abuts a staircase you do not need to cover the entire open plan area with detection, just the bit near the door to the staircase or escape route.(note 5 to   clause 8.2)

[Galeon]

It was practice before to have detention either side of a fire door (1 metre) that was retained upon by a magnetic , however if your system was of an L1 type , this was relaxed due to the heavily populated amount of auto detection.  What you need to look at now is BS7273-4 (2007).
If you are looking at detection to a premises which had the doors, with retainers and no detection , you will have to take this document into consideration.

[Wiz]

Surely, it could be argued that because fire doors are used to stop the spread of smoke, then any fire door allowed to be held open by a magnetic device (that releases on fire alarm), should be 'protected' by automatic detection to ensure that the door is closed when smoke is in the vicinity. Otherwise what is the use of having the fire door in the first place?

There was a 'fire officer's recommendation' that any such automatic detection be placed within 1.5m of the door, but it has now been decided that 'normal' spacing recommendations are sufficient - so it could now be 7.5m away from the door.

[Galeon]

Fair comment Wiz , that's why I said What you need to look at now is BS7273-4 (2007).

[David Rooney]

I have a CACFOA document (pdf file but I can't copy from it ...!) dated from 2003... may be out of date now, but it says that if you have magnets on doors ion an escape route, you should have a minimum type L3 system throughout.

The practice of dedicated detectors either side of the door should be discontinued as smoke entering the corridor could be "cold" and therefore not have the bouyancy or directional flow to reach the detectors by the doors.

This document may be out of date but has the thinking changed

Its only short.... any one want a copy your welcome to email...

[jokar]

The idea was that AFD operated the doors and it may have only been the AFD in a Cat M FA system.  If AFD is installed then the idea of additional detectors near the doors is impractical.

[Wiz]

The idea was that AFD operated the doors and it may have only been the AFD in a Cat M FA system.  If AFD is installed then the idea of additional detectors near the doors is impractical.

I wouldn't say 'impractical', but it is now considered 'unnecessary' since if the 7.5m max. distance is sufficient for any other location, then it must surely be also suitable for a location using held-open fire doors.

Also I would confirm my proposal that electromagnetically held-open doors should always be protected by automatic fire detection within 7.5m and which should release the doors in the event of detection of smoke. Furthermore, that whilst this may be as part of a higher category system, it could possibly be equally valid in a M system where just held-open fire doors are protected by automatic smoke detection and the system would therefore become M/L5 with an explanation that the L5 relates to the detection around the 'held-open' fire doors.

Does anyway disagree that electromagnetically held-open doors should always be protected by automatic fire detection within 7.5m and which should release the doors in the event of detection of smoke?

[Thebeardedyorkshireman]

If my memory is not totaly shot to pieces, this requirement came from Scotish building / fire regs and found it's way south. It then became part of fire 'custom and practice' and used to be specified by everybody because they had seen it on the last job!!!! The other posts are correct, however you should consider 22.2 c) of 5839 2008 if the door in question opens into a flue-like structure.
Regards
Dave

[Wiz]

Fair comment Wiz , that's why I said What you need to look at now is BS7273-4 (2007).

Galeon, I've had a quick look at it on-line and WOW! it's complicated.

It includes pages and pages of 'what if's' and the warning that the information provided in the recommendations is unlikely to enable an L5 system to be installed without a further fire risk assessment of likely smoke behaviour. There are also 'what if's' regarding door types installed to adjacent rooms etc.

This Standard is going to become another area of hard-earned expertise for those involved in designing fire systems. We will have to learn it because it contains many important considerations.

Sorry guys, but all of you who don't have access to this standard for free, are going to have to shell-out more hard-earned dosh on it, if you hope to be able to say you can design fire alarm systems.

Now where did I put my shares in BSI - They must be worth a bomb!

[Galeon]

Wiz ,
War and Peace may be a shorter read , I wish I paid attention at school to all those Janet & John books.

[Taiter]

Thank you for your comments in relation to my query.  To clarify then, where there is adequate detection within the corridor, that meets BS 5839 Pt1, there would be no requirement to have a detector head sited close to each door (within 1-3m) which is held open by a magnetic device.  Where detection meets BS 5839, the spacing would be sufficient to activate the magnetic devices.  Thanks.

[jokar]

Yes