Automatic Fire detection in Basement Loading Bay

[AnthonyB]

The situation;

Very Large Loading bay/Infrastructure area at basement level of large site with several separate buildings above.

Single stage Fire alarm to this area with optical smokes throughout linked to a Colt mechanical ventilation system.

Problem is that it goes off all the time due to vehicles exhausts and similar. (not linked to an ARC fortunately).

Option of switching to heat not OK as will radically slow down triggering of smoke control and will lead to the area being smoke logged before it fires up (area has several MoE from buildings above ,including a swimming pool going into it).

They already have a search period before dialling 999 & evacuating the area, which I'm going to formalise by having the panel reprogrammed to a two stage with intermittent sounders, overridden by time out, second head or call point.

Other than this are there any different detection methods that will still respond relatively quickly without being set off all the time by vehicles? (Ideally point detectors as a drop in replacement for existing heads)

[kurnal]

Do lorries drive into the area covered by the detectors or is it mainly Fork Trucks?
What is the approximate ceiling height?
Have you considered multi sensor heads? Or beams?
Is the Colt system for general ventilation or for fire ventilation?
Is it sprinklered?

If lorries start up under there with those dirty great chimney stacks they all seem to have nowadays then you will have all on stopping the false alarms unless you do something radical. But if lorries do go down there how do they keep the particulates under control?

[Graeme]

as Kurnal mentioned-Multisensor point detectors are a good option.

Beam detectors would be open to activation by the forklifts if they go up to high racks and also pigeons etc.

[messy]

What about the video detection systems. (VSD)

I come across such a system in a waste transfer station which had up to 8 trucks tipping waste and two wheeled excavators in use. I must be honest that I know vey little about them but was very impressed by what I saw at this filthy/dusty/smokey site.

(something similar to this http://www.ad-group.co.uk/companies.php?company=6 )

[AnthonyB]

No fork trucks, just lorries - it services restaurants, hotel/leisure, offices, etc.

Height about a metre over the height of a 7.5 tonne box lorry.

Not sprinklered and because of the 'nnnnnn' pattern of the concrete prefab roof sections  and the depth of each'n', has loads of heads, one per 'n' so very easy to be under one.

The Colt appears to be for fire only as is only triggered by the fire panel, am trying to find build fire strategy for clues as to what the set up is, as usual it's detective time!

Multisensors was my thought, ultimately some forced ventilation will be required for general use as the natural ventilation at the moment through the entrance road and the open end of the loading bay where the next phase is being built won't wash when the area is bigger still with only the service road to open air.

Oddly the transformers have Protec Sirrus (aspirating detection) in, which are getting clogged up all the time.

[kurnal]

Personally I would strongly urge them to do some fire modelling of the existing structure before considering extending it.

[Davo]

AnthonyB

We fitted beam detection in our main garage, then had loads of false alarms.
Discovered the strobes on the breakdown trucks bringing dead police cars back were setting it off.
Something to do with the beam being scattered
Still trying to figure out our next option

davo
davo

[AnthonyB]

There are a lot of questions on this job as there is no sign of the designed in fire strategy to explain how it is meant to work and I'm trying to dig it all up.

Most basement Loading Areas are only secondary MoE from staff areas if MoE at all, but this is complicated by including general occupiers & the public. As it stands if the fire is in the basement bay there is nothing to stop people leaving their area into the fire zone, so I'm advising do not enter beacons at exits into this area and that the adjoining buildings adjust their  own procedures to account for this route being out of use. It's a mess yet it's newish build.

Worryingly the first phase has been around for a few years and only now have they asked for a fire procedure for the infrastructure area and I've found there is no FRA and will have to do that as well.

Trying to write a procedure is difficult as the cause and effect of the fire systems is complicated as all the buildings  into this area are separate entities with their own owners/occupiers, so they are responsible for their own fire matters. This is why we are only required to do a procedure for the basement, rather than the whole complex, although a lot of co-operation & co-ordination will be required between all parties so that the various procedures. match up together.

[kurnal]

AnthonyB

We fitted beam detection in our main garage, then had loads of false alarms.
Discovered the strobes on the breakdown trucks bringing dead police cars back were setting it off.
Something to do with the beam being scattered
Still trying to figure out our next option

davo
davo

Hi Davo

I would be very interested in any further info you have on this phenomena- like was it only strobes or did rotating beacons have the same effect, did the beam system manufacturer investigate and were different configuarations of obscuration and duration tried before scrapping the system?

I am curious whether the strobes beams were interfering with the reception of the infra red beams,  whether the strobes were emitting radiation  that through phasing or something was cancelling out the beam or or whether the beam was being scattered as you suggest. Fascinating.

[CivvyFSO]

Is there any particular reason why CO detection would not work?

[wozzer38]

CO detection would be far too sensitive for this area and false activations would be rife. They are detecting at around 50ppm and any trucks exhaust fumes would set them off.

Plus if its a large open area >50m squared then the diffusion of CO would make them fairly pointless.

Best solution is to use Multi sensors...probably with Discovery capability so that sensitivity levels can be changed and 'day/night' modes could be used to automatically change sensitivity at critical times.

[CivvyFSO]

I have seen CO detectors in place that are also utilised for the standard ventilation, controlling the CO levels from fumes, and once it hits a level suggesting fire it ramps up to 10 air changes and sets the alarms off. The diffusion shouldn't be a problem in this scenario shoul it?

[wozzer38]

not a problem in that scenario because that must be a specific system set up for ventilating CO from an area.

Important distinctions should be made; there are really three types of CO detectors:-

1. CO Fire Detectors - Looking for about 50ppm CO and will detect it instantaneously. They may have 30-60 second time delays (integrating periods)

2. CO Environmental detection - Looking for anything between 100 and 300 ppm CO over a longer period of time (perhaps 5-30 minutes)

3. CO people protection monitors - Looking for up to 1000ppm again over an even longer period (perhaps up to an hour)

CO Fire detectors are for detecting CO from fires and are calibrated only just above normal background levels of CO and. therefore, small rises in amounts of CO from vehicle exhausts and even gas boilers will activate them.

[Thebeardedyorkshireman]

Anthony
You could try VESDA. Yes I know blah blah blah......We have a number working in Basement car parks. Ask Davo. !!! I tried to set it of with my landrover 85K miles Diesel.Smokes a bit when you set it off. System works perfect and the roof rack just clears the ceiling. Worth doing a trial with a length of pipe and a temp set up.
Kurnal/Davo. Yes its one of mine and has been driving us all nuts for some time. Turns out that the infra red element frequency of the light emmited by the stobe is within a knats of the beam frequency. We have a beam set ready to be rigged up to do further tests and I will let you know the results if we can simulate it here. This is the first time I have encountered this one and I have been at it since 1973!!  At the moment we just dont know if the problem is restricted to loop powered beams or extends to more conventional beams. We dont know if its just stobes or rotating but we suspect the former. Davos guys have been fantastic in helping us tract it down and it could have far reaching consequences for our industry. As a general plea anybody else had it
Dave

[Davo]

TBY

Any update on this, please


davo