Secondary System

[concretejoe]

Hi

I've a quick question regarding 'secondary' detection systems. We have a single floor in a multi-flooring office building (4 floors). The building is already fitted out with several detectors and sounders on each floor, regularly tested and (I presume) fully compliant.

We are making one of our rooms into a comms room in which we'd like to install a gas-suppression system (fm200\novec). I figured, because the room already has the necessary sensors, linked back to the central panel - it is compliant. Is there anything to prevent us installed an 'additional' system in the room - with its' own detectors (possibly VESDA) but restricted entirely to the room, and not back to the central panel. I figured, if this system detects a fire (e.g VESDA) the gas will trigger and the floor alarm will sound. If a fire does develop, and the normal building systems detect it (Which they should) then the building system sound. Obviously I wouldnt want the whole building being evacuated if the VESDA has a false-positive.

The only stuff I can find in the BS regs is a 'mixed system' for multi tenant buildings. Are there any problems complimenting an existing system with a secondary system for a confined area?

Cheers

Joe

[kurnal]

No I think you are looking at this the wrong way. This is my opinion only though- dont take it as gospel.

The gas suppression system would be best set up as a stand alone system with its own stand alone detection system - be it point detection or vesda, they usually have double the  detectors of a normal environment and operate on a double knock basis- two detectors have to operate to initiate gas discharge.

The suppression system then has an interface to the building main alarm system. This keeps the two functions connected yet independent. I have seen it done the other way in which the primary detection and alarm system is configured to trigger the gas suppression system and - in my experience- its a nightmare. When you have a malfunction or fault you end up with two engineers each blaming the other. When gas gets dumped accidentally its expensive.

There  are a number of standards for gas suppression systems, I believe these may be of interest though may be out of date or incomplete:
BS6266: Code of practice for fire protection for electronic data processing
installations.
EN 12094 part 1 for the control equipment   BS6387: Specification for performance requirements for cables required to maintain
circuit integrity under fire conditions.
BS7273: Code of practice for operation of fire protection measures
BFPSA: Code of Practice for Gaseous Fire Fighting Systems
NFPA 2001 : 1994 Standard on Clean Agent Fire Extinguishing Systems


Take a look at Tyco Inergen systems and also consider Wagner Oxyreduct for this sensitive area.

[Ashley Wood]

My advise would be to (as Kurnal says) have a separate system protecting this area. I would go for conventional point type detectors on a 'double knock' or coincidence principle. this means that if there were 2 detectors, each would be on a different zone. It requires both detectors to go into a fire condition to discharge the systems. By all means use vesda but only as an early detection system. The vesda shuts down the a/c creating a still air environment. The normal detectors then can function better. This system would have its own control panel outside the room with a key switch to enable you to switch the system to manual (when the room is occupied) and automatic (when the room is unoccupied). The panel will also have a manual activation button so that the system can be discharged manually. In addition the panel will have a status indication to tell you what the system is doing. All of the items I have detailed are required to make the system compliant with British standards. If you just connect it into the existing system it will not meet BS.

Also, remember that you will need to provide a low level extract unit to remove the discharged gas and by products of combustion. Also, you will need to make sure that the room is sealed up tighter than a ducks what's it otherwise you will loose your gas through gaps in walls, doors, sockets, etc. It may pay to do a pressure test but this will cost a few hundred quid. also, if you decide to go down the route of an inert gas make sure you have allowed for pressure relief otherwise when the system goes off it could blow out your walls/ceiling/windows.

[concretejoe]

Cheers for the replies.

Some more background (after reviewing the notes). The proposed system will be standalone, with its own panel and a double-knock effect in order to trigger the gas (Novec).  The bit I'm confused about is the room is already protected by the building system, I guess there is no harm in complimenting that with a standalone system that triggers the gas. The VESDA aspect is where I am confused - given it is very sensitive is it worth using that has a factor in the double-knock or simply use the VESDA to trigger a call out.

Is it worth interfacing the two systems together, and what would be the benefit? Do systems from different vendors play well together, from an interoperability standpoint?

[AnthonyB]

If the room didn't already have detection from the central system in it, we would require the computer room's panel to be linked so that in the event of a fire and gas discharge a building evacuation would be triggered by the central system going off.

Reasons for this are:

- we can't rely on tenants smashing a call point
- if the tenant's suite is empty, the rest of the building may not be and a link to the central alarm is required because there is no one in the tenant's floor to break a call point
- Many tenants forget a fire can occur out of hours and don't fit a Redcare link, by being linked to the central system then there will be a response from either the central systems Redcare link or the landlord's 24 hour guard

Interestingly I often find that although several server rooms have a VESDA or similar added by tenants a significant number don't have a gas system as well.

[kurnal]

Joe you have some decisions to make.
How critical is the comms room to business continuity?
Is there a process or data stored there without which your business could not function?
Is protection of this area the best solution or is it better to duplicate or have a back up of data or comms off site in hot standby?
If there is a fire or breakdown in the comms room how long would you be down and what is the potential cost of this?
How serious a risk of fire is there- comms equipment is pretty low hazard stuff usually its the consequences of a fire that may be the serious risk to a business?
If you recognise the comms room as business critical then do you need to protect it from a fire outside the comms room as well as from a fire within?

VESDA will give you the earliest warning of a fire in its incipient stages. One of the famous stories in the industry concerns the NATWEST bank whose vesda system was giving warning of component failure  two weeks before  it caused a fire. If you want that level of protection, and if you are sure all other business continuity issues such as those listed above have been considered, then vesda may be for you.

But if it  really is  that critical I would consider Wagner Oxyreduct which gives you detection and prevention of fire.

I see loads of comms rooms where much investment has been made in vesda, FM200 et al without considering the basics, usually these decisions are made by IT experts not fire risk assessors, and the investment is wasted because they have looked at the technology of the system and not at the risk of fire.

[David Rooney]

Cheers for the replies.

Some more background (after reviewing the notes). The proposed system will be standalone, with its own panel and a double-knock effect in order to trigger the gas (Novec).  The bit I'm confused about is the room is already protected by the building system, I guess there is no harm in complimenting that with a standalone system that triggers the gas. The VESDA aspect is where I am confused - given it is very sensitive is it worth using that has a factor in the double-knock or simply use the VESDA to trigger a call out.

Is it worth interfacing the two systems together, and what would be the benefit? Do systems from different vendors play well together, from an interoperability standpoint?

There is no harm leaving the "house" detectors in the room and installing your new detectors connected to the coincidence panel. Except you could end up with one detector going off before another and potentially causing confusion.

You could link the "gas system" into the house so that it sets off the house system on first stage (single detector operated) or on second stage (two detectors operated and gas about to dump).

You could use the VESDA system to activate the first stage alarm if required but this is very sensitve - as Kurnal says, how imortant is the room... is there 24 hour manned support... if not, is there any point in the vesda ?

Otherwise, keep the vesda separate to bring up a local alarm.

... and don't forget you may need an additional sounder from the house system in the comms room for warning of an alarm originating from outside.

[wee brian]

If you have a fully compliant building in terms of fire safety and you then decide to add a fire suppression system for property protection then there is no legal requirement to link the systems.

But it would be a good idea.

As Kurnal says, a VESDA can pick up an incident before it starts and somebody can go and find the cause (I had one where it picked up an overheating resistor on a PCB).  This only works if somebody knows what the kit is doing. You dont want to dump a job lot of fm200 unless you really have to.