Which extinguisher for machine workshop

[Guest IanRop]

Hi,
I was wondering if you might be able to offer some advice on what sort of fire extinguisher we should use in our workshop. It's not well ventilated so we were looking at something other than CO2. The main fire risks seem to be from use of flammable liquids (sparks reaching machining lubricants such as oils, and things like paint and the like), and a small risk of electrical fire if there is a major fault with the tools (milling machines/lathes). I was thinking that probably foam is best for our requirements in this case, or maybe powder, but was hoping you might offer some advice.

Thanks

Ian

[AnthonyB]

Don't over estimate the risks from CO2 portables, you are only generating a couple of cubic metres of gas and for this to be harmful the area would have to be so small the fire effluent would have taken you down first.

CO2 is great for machinery as being gaseous it penetrates hidden areas and casings to extinguish the fire and is non damaging thus reducing the effect on business continuity as it doesn't wreck the machine or require a full strip down to clean.

It also is effective on small Class B fires and even the smallest CO2 extinguisher has been tested on and extinguished a test fire of 34 litres of aviation fuel/water mix.

I'd keep the CO2 and back it up with foam. Foam cools and is good for solids as well as liquids and forms a blanket (like a layer of bubble bath) on a liquid fire preventing reignition. It's also good for spillages of flammable liquids - spray foam over the spill and it cuts off oxygen to the fuel and traps vapour meaning the spill can't be ignited making clear up safer.

Most manufacturers don't mark foam extinguishers as safe for electrical fires even though they can, so are mostly only marked as safe for accidental contact with electrical equipment unless you buy Britannia extinguishers (either the traditional Blazex or the low maintenance P50) which are marked (like most extinguishers on mainland Europe) for direct use up to 1000V

I'd avoid powder unless there is a realistic prospect of spilling and igniting a large amount of liquid as:
- The discharge will fill your workshop with clouds of powder which obscures vision, so you can't see what you are doing

- The powder is a respiratory irritant and breathing it in is not very good for you, you will be coughing and having breathing difficulty in a indoor area

- It is acidic and fuses when hot sticking to surfaces and is very damaging to aluminium, electronics (and most other things!) and will cause a lot of secondary damage - you will need to strip equipment down quickly to remove it before the damage is too bad and you will never get rid of all traces of it

- It extinguishes by a chemical action and does not cool or smother with a risk of reignition. If you don't extinguish a liquid fire before the extinguisher runs out it will often re-flash to original size & intensity (Foam, being a physical barrier allows partial extinction)

It's really good for rapid knock down of big spills but is flawed for other risks.

[Shawn Bosworth]

Hi Ian

An alternative to foam and CO2 would be the Jewel Saffire Dry Water Mist series extinguishers http://www.safelincs.co.uk/e-series-water-mist-fire-extinguishers/

These extinguishers are suitable for most types of fire, including flammable liquids and fires involving live electricity. They are also one of the safest extinguishers to use as they contain only de-ionised water.

Powder extinguishers used to be the most versatile extinguishers you could get but as they are no longer recommended for indoor use, the Water Mist extinguishers have taken over from them.

Kind regards

Shawn

[AnthonyB]

Water mist extinguishers are not marked as suitable for Class B fires as they do not meet the minimum ratings required by EN3 for the amount of agent - your existing CO2 extinguishers have a greater fire fighting capacity - the 6 litre water mist only has a 21B rating, a 2 kilo CO2 34B (or even 55B if fitted with a Zahan Frost Free horn). They are also more expensive and aren't offered by most suppliers.