AFFF extinguishers

[Bert]

Are AFF extinguishers safe for use on electrical apparatus, and are there any records of people being hurt (electrocuted) by using them?

When they were first introduced to the UK market AFF extinguishers were advertised as being safe for use on electrical equipment and labelled as such.  The claim was based on the method of delivery which, being via a spray nozzle, breaks up the flow of extinguishant thereby preventing a continuous electrical path between the user and the electrical apparatus. Within a year or so the “safe on electrical equipment” label was removed from new AFFF extinguishers.

However, trawl through the web sites of various extinguisher suppliers and you’ll find some claiming that these units are safe for use on electrical fires, some stating that they must not be used on electrical fires, and I even found some that said they were safe if used at a distance of one meter or more. What is the truth?

It’s interesting to note that so far as I can ascertain the UK is the only country that routinely uses’ AFFF and CO2 in combination rather than ABC dry powders.

[fireftrm]

No extinguisher should be used on live electricla circuits. Some AFFF, and indeed water, extinguishers have had the electrical conductivity test and are marked as being safe for ACCIDENTAL use on live circuits., bu this is by extinbguisher manufacturer and nothing to do with a generic type. So it is not possible to say that AFFF extinguihsers are, or are nor, safe for use ACCIDENTALLY on live circuits. You must check with each maker, and either way assume that electricity and water mix rather too well and are, therefore, to be kept apart. The basis of the test is to check the conductivity along the spray stream form the live circuit back tot he handle of the extinguisher, however many other variables could be in place at the actual fire, wet floor from usingt he extinguisher and differig footwear, examples that can have as much, if not more effect, than the stream of extinguishant.

You are right about the UK use of water based extinguishers alongside CO2. Powder would do both, but risks the mess and visibility problems that can be avoided by using aqueous extinguishants. How many people think about rendering the hazard and risks of live circuits safer through adoption of RCDs rather than CO2, or ACCIDENTAL use safety of AFFF/Water? Doing so would be far more appropriate.

[AnthonyB]

Most manufacturers will not mark AFFF as electrical safe (lightning bolt logo) although UK Fire (Britannia/Blazex range) & Total are notable exceptions.

Thus if you install AFFF for specific electrical cover and train staff as such with a brand of extinguisher not so marked you are personally accepting civil & criminal liability should an accident occur.

To safe me cutting and pasting from another thread a more detailed discussion on this subject is already on the forum, just do a search

[slubberdegullion]

There are two main problems with AFFF on electrical equipment.

First, electricity may travel up the spray if the nozzle does not cleanly ensure that no pathway exists.  A bit of grit might be all that is required to cause a solid stream to travel from the extinguisher to the live conductor.

Secondly, and more likely to be a problem, the operator of the extinguisher will be putting live electrical equipment in a puddle of conducting water and the operator may themself get wet hands or clothing.  If no circuit breaker trips or fuse blows then there could be big problems.  

Even if an extinguisher says it it safe, it can only be referring to the first of the above points and not the second.

More or less what fireftrm said, really, I don't know why I bother...

Stu

[Richard Earl]

hi gents, as far as i was trained AFFF is only a safe extinguisher to use IN THE likely hood af fire starting near and electrical socket, as electricity cant travel up bubbles.

IT CANT BE USED directly on electrical units, only Co2 can.

thats waht i have been told for the last 10 years anyway??

see you all soon?

richard

[Neil G]

IT (foam) CANT BE USED directly on electrical units, only Co2 can.

thats waht i have been told for the last 10 years anyway??

richard

I thought Dry Powder was also safe to use on fires involving electricity? ...that's what I've been told for the last 20 years (but I have been wrong before)

[slubberdegullion]

IT (foam) CANT BE USED directly on electrical units, only Co2 can.

thats waht i have been told for the last 10 years anyway??

richard

I thought Dry Powder was also safe to use on fires involving electricity? ...that's what I've been told for the last 20 years (but I have been wrong before)

Usually ok for domestic voltages in the UK

Stu

[Ken Taylor]

- but tends to lack the penetrating quality of CO2 and other gaseous extinguishant.