L5 Category

[Sherpa]

Is any one seeing a move away from the prescribed requirements of L1,L2,L3 & L4.

When considering detector locations, more and more of my customers seem to put what they want, where they want, and then call it L5 life safety detector layout.

My understanding is that an L5 detection layout would have to be a very carefully considered design, carried out by a fire engineer.

Any thoughts please.....

[kurnal]

I think the concept of L5 was to cover specific locations where automatic detection would not normally be required to be installed but in the circumstances it had been decided that automatic detection could be used as a trade off instead of meeting some other structural requirement or allowing an extended travel distance.

But like you sherpa I am finding the system abused, especially where the installation engineer  is not satisfied that the design meets the the letter of BS5839  - rather than discussing the variation with the designer or simply issuing the commissioning certificate with the variation declared the engineer has classified what is actually say an L2 with variations as an L5. In my view this is down to either laziness or ignorance by the installation and/ or commissioning engineer thinking they are covering their backs.

And its not getting picked up by the architects, clerks of works or building inspectors.

[David Rooney]

I think the concept of L5 was to cover specific locations where automatic detection would not normally be required to be installed but in the circumstances it had been decided that automatic detection could be used as a trade off instead of meeting some other structural requirement or allowing an extended travel distance.

But like you sherpa I am finding the system abused, especially where the installation engineer  is not satisfied that the design meets the the letter of BS5839  - rather than discussing the variation with the designer or simply issuing the commissioning certificate with the variation declared the engineer has classified what is actually say an L2 with variations as an L5. In my view this is down to either laziness or ignorance by the installation and/ or commissioning engineer thinking they are covering their backs.

And its not getting picked up by the architects, clerks of works or building inspectors.

Totally agree. Also think that the vast majority of the above named professions wouldn't know an L1 from an L4. I don't think they care as long as they have a piece of paper in their hand so they can lay the "blame" somewhere else.

And the piece of paper could be a toilet roll, because they also don't know what certification to expect.

Since 2002 we have never ever ever been asked to supply Design or Installation certificates to anybody.

[Wiz]

Kurnal and David are Spot on with their comments. L5 systems are designed to satisfy a specific fire safety objective based on a fire fire engineering solution. It is my understanding that such a solution would also need to be described in writing and form part of the category description for an L5 category for it to be acceptable.
If you ever see a request for an 'L5' system then always ask for a written description of the risk identified and the solution engineered to overcome it.

[Midland Retty]

Yes I too have to agree with your comments.

Category L5 must not be used as an excuse to justify a cost cutting excercise or substandard fire precautions.

My brigade / authority is now looking into the prospect of realing in more installers and RP's to account for naughty little things like this.

[David Rooney]

Yes I too have to agree with your comments.

Category L5 must not be used as an excuse to justify a cost cutting excercise or substandard fire precautions.

My brigade / authority is now looking into the prospect of realing in more installers and RP's to account for naughty little things like this.

Damn right..!!

There is nobody who seems to police the certification of fire systems anymore. The end user generally doesn't have a clue what to expect and the average installer still seems to get away with scribbling a name on the back of a fag packet.

[AnthonyB]

Category M with L5 enhancements - that's what I saw in a very big national fire alarm company's commissioning certificate for a new system. It was basically meant to be an L2 but they made a pig's ear of the 'areas opening onto MoE' bit which explains the change in cert. Wasn't picked up until a couple of years later as the cert had just been filed, not read.

L5 to me normally (but I admit not always) means a category M with the odd head here and there for things like access rooms, not a substandard 'almost' L3/L2/L1

[Sherpa]

Glad to see its not just me!....It seems the L5 category is been abused, maybe it should not be called L5 and should be changed to S5 (special 5).

Because its called L5, customers believe they have a system designed around life safety, however an L5 design can fall well short of this. Its what ever the designer wants to put in and there are no wrongs or rights.

I also agree with David Rooney that the whole certification side of things has deffo gone down hill. I find it increasingly difficult to get someone to take on design responsibility and issue the appropriate certificate. Equally the installers normally also look quite blank when you ask them to issue a BS5839 install certificate.

I would be very interested to read any published articles on the true intent of the L5 category, is anyone aware of such articles?.

[kurnal]

Not seen any articles or guidance on this other than for the manufacturers design guides (some of which are not helpful - eg the ADT design guide gives an example of the use of L5 in compensation for a lack of structural fire resistance but they do not give any further detail or explanation on how and with whom such trade offs may be agreed.)

Most of the others eg Gent just give a one line explanation of the category. In the absence of proper certificated design as seems widespread from this thread its not surprising that the category is being abused.

I attended an ADT seminar a few years ago delivered by Colin Todd and still have a copy of his hand out which, still only a paragraph, explains the intent very well and would be happy to fax you the relevant page if it would help. But it wont tell you any more than you already know.

[Sherpa]

In your opinion, who would be QUALIFIED to carry out a L5 category design layout?

[William 29]

I agree with comments posted so far in that generally L5 systems are abused.  I also think that many fire alarm designers are afraid of commissioning L5 systems as they are unsure of how to meet certain specific fire safety objectives.  They prefer to go for L1 to L4 as the location of detection is more prescriptive, easier to design and then commission.

I would suggest that a competent or (qualified if you like) person to design an L5 would be a competent fire risk assessor with some fire alarm knowledge and design training such as the BAFE course in fire alarm design.

In my experience an L5 system is quite straight forward.  You can have a pure manual system say for an office with one smoke detector to cover an inner room or detection to compensate for lack of fire resistance in a dead end.  It may also be used to compensate where the travel distance exceeds the recommended norm or a deviation from a building regulations requirement.  

BS 5839 states that the design of any system should be based on the outcome of the FRA.  In conjunction with the fire alarm installer the commissioning certificate should clearly state the rational and objective of any L5 system.  What tends to happen is the alarm system is designed and installed first and the the FRA is an after thought……in my view

[kurnal]

In your opinion, who would be QUALIFIED to carry out a L5 category design layout?

Thats a difficult question and there are two aspects to it.

1- someone who is qualified to recognise the life safety implications of the building- how it is to be used, who is to use it and  who may be at risk, any variations from benchmark design standards and  their effect on the life safety of all who may find themselves affected should a fire occur in this building (including firefighters for Building Regulations approval).

This person must determine the equivalence of any fire safety solution they install such as a category L5 alarm system to a code compliant design.

This person could be an architect,  a fiire consultant or a building control officer / approved inspector and sometimes all three will be involved in determining the category in the first place. All these people should have a detailed knowledge of design codes and benchmark standards and a level of fire engineering to some extent but probably wont know their firetuff from their end of line resistor when it comes to system design.

2- The actual alarm system  layout must then be designed by a competent fire alarm design engineer - probably the M&E contractor- taking into account the detail of the installation, the actual provision, number and siting of alarm system components to meet the requirement identified by the building design team and the BS.


I know thats ideal and is cobblers compared to real life. Most likely an architect will put a few detectors on  the plan and a sounder here and there for good measure and give to to the local sparks - or indeed just tell the sparks to install an L1/2/3/4/5 without any further guidance or design. And very often the choice of system category is more closely related to the budget available than a life safety need.


I am often asked to carry out fire risk assessments in newly erected buildings and am sometimes  at a loss to understand the fire strategy. Very often the design has been agreed between the architect and approved inspector and sometimes these are employed by different divisions of the same firm.

I have heard clients say to approved inspectors - if you dont approve this you wont get the next job.

I have seen designers and approved inspectors picking bits out of DD9999 that they like and ignoring the caveats and the bits they dont like. I do have some concerns for the industry.

[Graeme]

The whole L5  thing is a nonsense. When a customer comes to me and informs me that they have been asked for an L5 but cannot get official guidance they then ask me.
I am unwilling to do it ,so they then do a design on their own "risk assessment".

Like Dave mentions-who's responsible now for producing a design certificate?

As with more installs now that customers do not want the responsibility for the design so go for all over coverage,where a professional risk assessment could reduce it.

They can't win.  Pay for a pro risk assessment and then get a reduced coverage or get blanket cover without the cost of a pro risk assessment  cost.

[William 29]

Surely the cost of a pro FRA as you put would not compare to the difference in cost beween an L1 and L5 system?

[Graeme]

customers don't see it that way. They do not wan't to pay for a fire alarm system in the first place without the cost of a RA too.

Things were much better when the Fire Officer did them and told the customer what coverage he needed insted of now where no one wants to take the responsibility.