When is a L4 AFD System the Right Choice???

[Messy]

My GP's new, large and rather posh 3 storey surgery appears to have a L4 AFD system, with what look like detectors in consultation rooms but are actually just sounders. Firecode seems to say that all patient access areas should have L3 or L2 which makes sense, so I am not sure how he got into this situation.

I rarely see L4 systems, and have never recommended one. So in what circumstances would you (or have you) recommended a L4 system as I cannot imagine many circumstances why such coverage would be deemed suitable. But L4 remains in BS5839, so I assume there's a use somewhere out there?

[Bill J]

In a fully occupied office BS5839 suggests a manual only system would be acceptable for life safety, where there is a need for electronic alarms to ensure all persons are made aware.

Assuming that all rooms open onto a protected escape route, and are normally occupied by persons awake and active, (Office block) for life safety a category L4 is an improvement on a Manual only.

I guess it would become essential if it was possible that occasionally one of the rooms opening onto the protected corridor could be unoccupied, (For example an unlet office or a staff holiday), therefore putting other persons at an increased risk of a developing fire. The cost to install detection in every office could be considered prohibitive.

I am also seeing a number of requests for L4 systems in the common parts of (stay put) residential blocks, linked to a central station, sounders throughout, but only activating after a time delay or a callpoint activation.

Bill

 

[AnthonyB]

We routinely specify L4 as a minimum in multi occupied office blocks or similar multi occupancies due to varied occupancy times and possible vacant areas where originally a manual system or manual with random AFD would have been on the fire certificate back in the day, based on the risk of a fire starting and growing in an area that was closed for the day and growing unnoticed until escape is compromised - as was the case in the multi fatality Murray House fire.

Various factors are considered in the building so in some situations there would be a need for L3 to give more robust protection to the escapes (especially if there is only one, or there are factors with the persons at risk), other buildings may have the L4 enhanced in specific areas (such as dead ends in lieu of fire doors as per the guidance).

L2 & L1 are reserved for high risk or complex premises as per the guidance or as part of an engineered solution (be it a full BS7974  exercise or the full application of BS9999) so in our main property types we deal with we only need to see L4 or L3 (but point out going further as an informed choice by the client as oppose to a 'legal requirement' because it isn't may have property protection advantages but comes with more enhanced false alarms management)

[Phoenix]

First of all, Messy, when you refer to 'Firecode', do you mean HTM 05/02?  This is not usually appropriate for GP surgeries as the guidance it contains is targeted at buildings with more dependent people than are usually found in a surgery or healthcare centre.  Unless there are justifiable reasons, I would suggest you use other guidance.

I'm with Anthony and Bill on the matter of L4.  I inspected a large office block a little while back that was all cellular layout with hundreds of individual offices off long central corridors with lots of staircases.  Ground and three upper floors,  Mainly 9 - 5 but some out of hours work.  An L3 system would have been way over the top so I recommended L4 to cover those periods when only a few people were in the building.

[Messy]

Many thanks to all. I hadn't come across many L4 systems, but can see how they can be useful in certain circumstances

I appreciate your replies

Phoenix: I was referring to HTM 05/03 part B which applies directly to NHS premises and as best practice to no NHS premises providing NHS care

[colin todd]

Davey, I invented L4 and I think its really cool. I am wounded that you never specify it. Dont hope to get a christmas card from me.

[Messy]

Davey, I invented L4 and I think its really cool. I am wounded that you never specify it. Dont hope to get a christmas card from me.

I apologise Colin. With respect, please don't send me a card this year, as the last few years you seem to have forgotten to put a stamp on and its costing me a fortune