Water based extinguishers in common areas of sheltered accomodation?

[Golden]

its not difficult to be honest - just needs some experience and conviction.

[kurnal]

All have been on the same course at the same time and all have come out with differing opinions.

Is that literally the case Reiver? It would be interesting to know what level of training that was and whether all attended the same course delivered at the same centre. Nevertheless a key outcome is that before embarking on a project of this nature it pays dividends to bring all the assessors together and set out the technical standards to be adopted for the client in question. Then if your standards are questioned later you can set out a uniform and well argued strategy. You will win your case .

[AnthonyB]

I could see the sense of Wet Chemical or Water Mist as you can't go wrong and they will deal with the various likely causes of domestic fire, however when you see outdated cumbersome Water Jet there is little point as it will only make things worse....

[lancsfirepro]

Always makes me take a sharp intake of breathe when people go about saying water-based extinguishers are safe for use on electrics just cause they've passed the 35kV test.  I suppose EN3 is to blame where it requires the manufacturers to mark an extinguisher with "suitable for use on live electrical equipment up to 1000 V at a distance of 1m" when it has passed the dielectric test.  Very bad form in my opinion and why BS5306-8:2012 clause 5.4.2 recommends not to provide water-based extinguishers for electrical equipment.  Fine for the odd splash here and there, but providing water-based extinguishers for electrical risks is a no-no.

[Tom Sutton]

Shirley to way to deal with electrical and gas fires is to isolate the supply and then use the appropriate class, which includes water, the only difficult or impossible situation, is the mains intake/meter cupboard/room.

I believe the clause in BS 5306-8:2012 is about when you are dealing with an A class fire and accidently spray live electrical equipment.

[lancsfirepro]

Yep, in an ideal world, every electrical fire should be isolated prior to using an extinguisher, but this will rarely happen (lack of proper training, panic etc).
Part 8 clearly states not to provide water-based extinguishers for electrical risks.  It also states that if extinguishers that have passed the conductivity test in EN3 "..inadvertently splashes onto electrical equipment, then the spray type discharge will afford the user more protection from electrical shock than the discharge from a jet type extinguisher or a spray type which has not passed the BS EN 3 conductivity test."  So, it allows for indirect use only.
Not just class A fires; could be a class A, B or F fire.

[Tom Sutton]

Why in there no class for electrical fires?

[AnthonyB]

There used to be unofficially - Class E (or if you go back long enough Class C)- but EN2 knocked that on the head as electricity isn't a fuel, just a hazard, so it was dropped in the UK & Europe where already used.

The US still has Class C for energised electrical equipment as does Australasia with it's Class E.

There is plenty of independent test evidence from the 1920's through to the present showing the safety of water based agents on electrical fires and the cases of user electrocution are largely from the days that wet extinguishers produced powerful electrolyte solutions on discharge (soda acid, chemical foam) and when electrical installations were simpler with less built in safe guards like RCDs.

At the end of the 1980's British Rail made a national changeover to remove halon for electrical & mechanical risks and begin a gradual phase out for water jet with a single agent - AFFF spray in TG 0.9, 1.75, 5.5 & 7.5l extinguishers. They didn't take the decision lightly!

A client has recently extinguished a 415v industrial tumble dryer fire with water mist portables when the CO2 originally placed for the risk failed to do the job (it's now replaced with a electrically approved water spray) with no issues.

A cynic would say that in line with some of the other changes in part 8 the approach to wets on electrical is to bolster the sale of CO2 rather than embrace innovation (P50 anyone?)

If a manufacturer won't back their kit up with the lightning bolt symbol and a clear commitment in labelling and paperwork as to it's safety for direct use up to 1000V then regardless of your opinion you have to stick with the accidental contact, there are a couple out there who will mark their kit this way though...

[Tom Sutton]

A cynic would say that in line with some of the other changes in part 8 the approach to wets on electrical is to bolster the sale of CO2 rather than embrace innovation (P50 anyone?)

The P50 is about construct using the latest materials and servicing. Would saffire water mist be a better example they claim it can be used on live electric but I still say isolate the supply is the safest solution using RCB or manually.

[lancsfirepro]

There is plenty of independent test evidence from the 1920's through to the present showing the safety of water based agents on electrical fires and the cases of user electrocution are largely from the days that wet extinguishers produced powerful electrolyte solutions on discharge (soda acid, chemical foam) and when electrical installations were simpler with less built in safe guards like RCDs.

I wouldn't dispute the fact that some water based extinguishers can be used to tackle fires involving electrical equipment.  Sure discharging water as a mist/spray won't conduct electricity back to the user, but what you need to be aware of is that the water you are discharging will be making a nice wet patch on the floor from the electrical fire to where you are standing.  Getting shocked through your feet anyone?
On an FRA, I'd pull any water based extinguisher provided for an electrical risk; regardless of whether that extinguisher had passed EN3's conductivity test or not.

[kurnal]

You really would have to be unlucky to receive a shock through your feet by standing in the discharge from an extinguisher. Particularly at 240 volts. Your body would have to bridge the potential difference either by standing with one foot in the pool and disregarding any insulation offered by your shoes to have contact with a well earthed surface outside the wet pool with another part of the body. It's the same as birds sitting on power lines.
As an aside  I recollect being instructed to direct a main jet of water onto a 30kv live power line about 30 feet away. All colleagues were instructed to hold onto the hose. This was a standard element in the Jo course at the fire service college.

[lancsfirepro]

You should know better than to use the word 'unlucky' in this business kurnal.

[kurnal]

I hear the risk of shock stated so often by so many and get frustrated that many people (not on this forum of course) glibly repeat the message without trying to analyse the underpinning issues.

I guess what I am saying is that I contend that the risk is overstated because it convenient to do so and because to err on the side of caution brings some easily won commercial advantage.

[Mike Buckley]

I recollect being instructed to direct a main jet of water onto a 30kv live power line about 30 feet away.

Yep remeber it well, a bit disappointing no flashes bangs or anything!

[Tom Sutton]

Another point to consider the saffire water mist extinguisher uses 100% de-ionised water.