Odd Phased Evacuation Set Up

[Messy]

I have come across a AFD system that is broadly a (basic) phased evacuation system.

However, instead of using a second detector head (or device) to escalate to the next phase, it uses 'any additional head in a neighbouring zone' to escalate

With up to 15 heads in a zone, it means that a fire would not escalate to the next phase even if all 15 heads in the initial zone where activated. But it would escalate if one head in the original zone and a second head in a neighbouring zone activated (see drawing).

This seems total nonsense but the RP has a commission certificate and is happy with his long standing AFD contractor

Any views?

[lyledunn]

Surely this all depends on the evac strategy which in turn will depend on the characteristics of the building and its occupants.
To be clear, a fire signal in a zone triggers an immediate evac warning to that zone but will not provide any kind of signal to neighbouring zones even if fire engulfs the original zone?
You refer to a drawing but no link given. What type of building and how are the zones configured?

[AnthonyB]

It wasn't in Scotland was it?

Did it have any manual zone by zone override set up as well?

Posted a similarly odd set up a few months ago, fortunately the new management weren't comfortable with it so agreed to move to traditional phasing.

[Messy]

Sorry my sketch was too large to post!

There's no manual override to escalate as an MCP is treated the same as smoke detector

No not in Scotland, but in the heart of the city of London

There is no recorded evacuation strategy for this premises. The building is old and the current RP has 4 x times the staff squeezed in this building than he did when he moved there 30 years ago. A simultaneous evacuation strategy would not work - we tried it a few weeks ago and the stairs were gridlocked - as I predicted but the RP argued with

The original concept that I found in an old dusty document was for a horizontal type evacuation as its a long building. That was dropped during the project to convert the building to offices and there is insufficient horizontal compartmentation (or space) to allow PHE now

It appears that the current odd system was bodged up as a panic when the PHE was abandoned. The building has been audited by the local enforcement teams, but if they got the same briefing as me, they would have not understood the reality as I didn't. Its only when large scale testing of the alarm system was carried out, the anomalies were discovered

I am not happy with it one bit and the RP hasn't got any cash to do anything with it

My employer has a contract with the RP so I can't walk away, but frankly there's not much else to do than to record my advice and walk away 

[Fishy]

I'm not at all clear on what type of evacuation we're talking about? 

If we go by the BS 9999 definitions, under phased evacuation the whole affected floor goes straight away (& the floor above, normally) - subsequent floors being dealt with under a management procedure, rather than an automatic 'all out' (other wise you risk clogging the staircases and making things worse).  PHE evac goes from compartment to compartment, normally with immediate evacuation from the compartment of origin.  Zoned evac is similar, but isn't necessarily associated with solid fire resisting barriers.  Phased evac is normally used in tall buildings; PHE in buildings with extensive floors and good compartmentation (hospitals being an obvious example), zoned in low-rise buildings with large open spaces.  All need really good management control & robust fire protection arrangements.

Sounds like this is zoned evac?

By the way, the RP are kidding themselves if they think that "...the RP hasn't got any cash to do anything with it... is even remotely a good excuse to leave thing as they are.  The law assumes that if you choose to do something, you've positively established that you can afford to do it safely.  Cost is a legitimate issue - affordability is irrelevant.