Electrical Fires

[MC]

During a fire risk assessment at a clients property , it was noted on the previous FRA that they had concerns that there was no provisions for fighting electrical fires on each floor level.  The property already has 1 x Foam and 1 x Water type on each level. Surely if in the event of a  fire and the power was isolated , this would not be classed as an electrical fire, and the current extinguishers would be sufficient.
Many Thanks

[nearlythere]

Problem you have is how does one know if the power is off. With electrical equipment one has always to make the assumption that it is live. In the spur of the moment it would be difficult to expect the average person to make a considered assessment as to whether it is safe or otherwise to use a media other than that as recommended.

When the alligators are snapping at your a@@e, it is difficult to remember that the reason you went into the pool in the first place was to pull the plug out .

[Big T]

As part of the risk assessment you will identify electrical fires as a significant hazard and mitigate this risk by requiring Portable appliance testing to minimise the chances of a fire starting, minimise combustibles around it to prevent spread and in my opinion install a CO2 extinguisher to extinguish a fire. Water and foam are all well and good but the reality is the general workforce will not know how to isolate the buildings supply or be able to do it quick enough, and asking the general workforce to get under a table with a burning computer on top of it is unrealistic. In a modern world I would go with CO2 to complement Foam extinguishers.

[Nearlybaldandgrey]

And not forgetting to have a number of nominated staff trained in the use of the fire extinguishers.

[Big A]

I can't help remembering a demonstration at Moreton involving a 70mm jet and a 30,000 V grid. Even with the jet at maximum power no current at all passed back down the jet. Isn't it the case that we all get a little hysterical about the risk of electrocution from small electrical fires?

Or am I mistaken?

[Mike Buckley]

Yes I agree we probably do get a bit hysterical about the risk, however the general rule of electrics and water don't mix has been well accepted and to try and change it for fire extinguishers will just spread confusion.

However the Moreton demo does come in useful when people start questioning the use of sprinkler protection with electrics and the use of water mist for computer suites.

[nearlythere]

I can't help remembering a demonstration at Moreton involving a 70mm jet and a 30,000 V grid. Even with the jet at maximum power no current at all passed back down the jet. Isn't it the case that we all get a little hysterical about the risk of electrocution from small electrical fires?

Or am I mistaken?

The matter of the electrical conductivity of water is very well known to all and sundry. Pure water is non conductive. The conductivity is dependant on the level of impurities contained in the water and the distance from the electrical source. The higher the impurities the more conductive it is. The conductivity of sea water is greater than fresh water because of the higher level of impurities eg. salt.
The Morton demo is obviously safe because the branch is a distance away from the grid and the water is fresh and relatively clean. If you started to move towards the grid or used sea water you would measure an increase in conductivity at the branch and as you got closer it would eventually be fatal.
To use a water extinguisher on electrical equipment from a distance may be OK but who wants to try it?

Sprinklers may not neccessarily be a hazard because the conductivity of a spray or water droplets would be very low. The hazzard comes from the water getting into electrical equipment, just as it would by using jets.

[MC]

Many thanks for your help

[AnthonyB]

Late to the debate, but it must be remembered some electrical equipment can retain a charge after being switched off.  Water & foam extinguishers in the main are not marked as suitable for electrical fires (with one or two smaller manufacturers being an exception) and thus you are going out on a limb if you use them against manufacturers guidance. In an emergency it's not always possible to be sure you've isolated the power & not always     easy to do without risking putting the fire between you & the exit, or by talking to long (& plunging the place into darkness or EL levels only) by going to the main consumer unit.

Someone obviously messed up as what's the point in having water and foam together as you are duplicating cover. Where there is a live electrical risk you need, if you are going to tackle it, an extinguisher marked as fit for the risk, i.e. the lightning flash symbol, should be supplied. After all we are not splitting hairs over what's more effective, we are talking a mortal risk here that has been recognised in extinguisher design since the 1900's.

For safety's sake go with a non-conductive agent.

On a historical note in the 40's & 50's Nu Swifts Universal (Royal Navy) Extinguisher with a jet/spray nozzle was sold as safe up to 500V and British Rail replaced Halon with Foam (although that has been overturned since in most of their former & remaining properties with CO2 being added)

[Big A]

I can't help remembering a demonstration at Moreton involving a 70mm jet and a 30,000 V grid. Even with the jet at maximum power no current at all passed back down the jet. Isn't it the case that we all get a little hysterical about the risk of electrocution from small electrical fires?

Or am I mistaken?

The matter of the electrical conductivity of water is very well known to all and sundry. Pure water is non conductive. The conductivity is dependant on the level of impurities contained in the water and the distance from the electrical source. The higher the impurities the more conductive it is. The conductivity of sea water is greater than fresh water because of the higher level of impurities eg. salt.
The Morton demo is obviously safe because the branch is a distance away from the grid and the water is fresh and relatively clean. If you started to move towards the grid or used sea water you would measure an increase in conductivity at the branch and as you got closer it would eventually be fatal.
To use a water extinguisher on electrical equipment from a distance may be OK but who wants to try it?

Yes, we do all know the conductive qualities of water. The explanation we were given for the lack of charge was that even a large jet under high pressure is still not a continuous line of water. The jet is beginning to break up as soon as it leaves the branch (even if not apparent to the naked eye). I am also assuming that the water contained in extinguishers is clean. (Again, am I mistaken?)
Is there any evidence or is it just 'something that everyone knows'?
I'm even less sure now that someone has mentioned the codes date back to 1900. Understanding of electricity was considerably less then. Could it be that the codes have just never been changed (rather like the 20m rule for turning circles -B5  max distance for horses walking backwards).

[AnthonyB]

Water used in extinguishers is 'as it comes' from the water supply on site -it could be mains fed, been stored in a tank first, been through lead pipes or anything.

It's certainly not pure and can contain all sorts of stuff. That is why with Water extinguishers designed especially for electrical fires, such as the Amerex Water Mist extinguisher, you are only supposed to use Distilled Water from sealed containers.

Extinguishers to EN3 (or more precisely their discharge) go through a 35kV conductivity test - if they fail they have conducted along the stream and they are marked as unsafe on electrical equipment.

Even those that pass (water & foam sprays usually) are not normally marked with the 'electrically safe' pictogram as there are too many factors that still present a risk not least the risk from pooled agent.

And although not the main factor they will cause more secondary damage to the electrical appliance than even powder does.

As extinguishers are now so ridiculously cheap these days (unless you are mug enough to use certain of the big national's for supply) is it worth splitting hairs over - just bung some CO2's in or if you aren't protecting escape stairs/corridors &/or a hotel/hospital/care home then replace the lot with factory sealed 2 kilo ABC Powders and save a fortune on purchase price and annual maintenance (which you wouldn't need)

[Paul2886]

Of course it all begs the question 'where are you going to be free of electrical risks in any room. There are sockets, wall lights, and many other electrical pieces of equipment. So, should we only have dry powder or CO2 in buildings and no water based extinguishers. What a nightmare that would cause.....I rather like AFFF foam spray extinguishers instead of water. Lighter to handle, give a wider coverage, less likely to conduct electricty back to the user. Of course MCB's will add considerable protection as opposed to conventional fuses. Don't we all have a marvellous knack of making a science out of everything...sigh

[fireftrm]

Quick point of concern is 'electrical fires' as for as long as I have ever studied the subject I have never found electricity to be combustible. What is mean t is much moire accurately described as a fire where live electricity is also present. Electricity can provide the spark, or heat, due to a fault to start a fire, but cannot be fuel for one.

if electical risks are identified then the risk assessment should not only look at the fire fighting provision, as that is further down the control measure lsit than removing the risk. Removal of the risk can be dealt with reasonably easily by ensuring that electrical circuits are protected by RCDs, these are designed to prevent the fire starting through electrical faults and to protect persons from electrocution should they come into contact with live circuits.

Do not think that a fire risk assessment means that only fire fighting/detection/signage are the available control measures. Dangerous, dangerous to stay on that line of thought. A fire rsik assessment is to identify risks and to suitable controls. Removal of the hazard/risk is always the best option and clearly the safest. So the RCD should be used first and extinguishers safe for use on live circuits only if this is not practicable. No electrical circuitry should be so unsound as not to be suitable for RCd fitment, indeed I suggest that the circuitry was probably not examined?

[John Webb]

Provided an electrical installation has been designed, installed and regulary tested in accordance with the IEE Regs (BS7671) then the risk of it being the cause of a fire is pretty low. Regular inspection/test needs specialised knowledge and equipment, so anyone carrying out a FRA on a premises should ask to see the latest Test Certificate for the electrical installation. If there isn't one the absence is a significant finding and should be appropriately commented on in the FRA.

[Chris Houston]

Provided an electrical installation has been designed, installed and regulary tested in accordance with the IEE Regs (BS7671) then the risk of it being the cause of a fire is pretty low. Regular inspection/test needs specialised knowledge and equipment, so anyone carrying out a FRA on a premises should ask to see the latest Test Certificate for the electrical installation. If there isn't one the absence is a significant finding and should be appropriately commented on in the FRA.

Don't overlook the portable appliances, including the ones that the staff have brought in from home.

Thermographic testing is a nice bonus to a full test.