Role of MCPS in phased evacuation

[alfi]

Hi all
a building with phased evacuation, this fits all the requirements of
> ADB such as sprinklers and compartmentation etc, however I note from the
> fire alarm cause and affect that any MCP will cause the fire alarm to go to
> all out and over ride the phased part, surely if the smoke heads are
> designed to operate under phased conditions which they do, why wouldn't
> MCP's?, so currently if any MCP is activated the whole building goes into
> simultaneous, but fire exits have been calculated on phased according to
> fire strategy, just wanted your thoughts.

ta

Alfi

[kurnal]

This does sound confusing - presumably this is an office building with the phased evacuation in the vertical plane? You mention fire exits are sized in accordance with the phased strategy - does this include the staircases? The system itself sounds to be set up as a staff alarm at present?

[alfi]

Hi Kurnal

Yes you are correct on both counts staircases size smaller  and vertical evacuation. I have looked at BS5839-1 2013 which just states any MCP's on the stairs must be linked to the zone they are located, I can accept that, but why on earth have all out on any MCP being activated, dfeats the object I think? 

[kurnal]

The MCPs should be in the accommodation at the door leading to the stairs and not in the staircase itself. If in the staircase persons may operate an MCP within a different alarm zone as they pass down the stairs!

You are right that operation of an MCP should normally trigger an evacuation signal within the alarm zone involved and an alert signal elsewhere. Set up as it is , if  the system went into full evacuation then it is likely that persons at greatest risk on the floor of origin will be obstructed as they try to leave via the already full staircases. This C&E needs review in accordance with the fire strategy for the building and BS5839-1.

[Fishy]

The fire system designers are probably being guided by Clause 19.2.2 c) of BS 5839-1:  "Staff alarms should normally be generated only in response to signals from automatic fire detectors, but not in response to signals from manual call points, heat detectors or sprinkler systems".

Could be subject to a variation, of course, if the fire strategy supports it & client and Building Control are content.

[alfi]

Thanks for input gents

not convinced this has been commissioned correctly so I have asked the client for a meeting with the fire alarm contractor, I think somewhere along the line human error on interpretation has taken place, so until I'm fully satisfied I have raised it as an action point in the FRA

[Phoenix]

It sounds to me like the common error of mixing up a 'phased' system with a 'staged' system.  In a two stage system the MCPs are often set up to go straight to stage 2.  You definitely want the fire floor to go alone.

[Mike Buckley]

Yes, I would agree with Pheonix, the basic principle being that detectors can send out unwanted fire signals and in some cases there needs to be an investigation procedure to determine that there is actually a fire before the premises is evacuated. It is assumed that if a MCP is activated it is activated by a person who has discovered a fire hence the need for immediate activation of the alarm. Although I have come across some circumstances where this is not the case normally because there is a high level of malicious activations of the MCP.

As kurnal said the last thing you want in a big building with a phased evacuation policy is for everyone to be turfed out at the same time in most high rise buildings the staircases just cannot cope with the extra numbers.

[Mr. P]

So, does your fra consider the number of malicious activations of MCP's? It is always possible for for malicious activities but, in reaality, how many times does this occur, by whom it is acivated etc? If employee, the company disiciplinary procedures, if from outside, then consider security issues of the premises. Earlier comments particulary Mike B hits the point though.

[Mike Buckley]

I would hesitate to actually put a figure on the number of malicious activations. The litmus test is does the client regard it as a problem?

This will depend on the environment, for example a hotel would have a lower tolerance of malicious activations, as opposed to a student hostel. In the former having the guests evacuate and stand outside too often will create complaints and possibly lose business. Whereas in the latter social pressure from the other students may a greater controlling effect.

In hotels another aspect could be the type of clientele, I would expect a higher level  of malicious activations in hotels which specialize in stage or hen parties as opposed to a family or business style.