Fire!

[Mary Fisher]

Today we had the need to use the small dry powder fire extinguisher from the caravan - not in the caravan.

I'd like to know what the powder is - it feels like extremely fine sand but it's also caustic and obviously has some kind of salt in it - I accidentally licked my finger.

I know that we're going to have to replace it even though we only used it for a two second burst (it did the job splendidly, if messily) but does anyone have any authoritative recommendations, please?

Our larger CO2 extinguisher was out of gas (it hasn't been serviced for years so that's not surprising!) and the other one we have employs carbon tetrachloride which wasn't suitable for the small conflagration we had. It was in a confined space so the resultant phosgene could have been nasty.

Mary

[<me9]

I was under the impression it was sodium bicarbonate.

The fire peeps allowed us to have one instead of a fireblanket when we were childmnding, but pointed out that they were extremely messy.

We used one on a burning TV set once, It put (blew) the fire out but it re-started as soon as the stuff cleared.

You must have had that one since Noah was a lad.__

[Grunff]

Bicarb. Used because it's cheap, has a high thermal capacity and relatively low toxicity.

For extinguishers? Screwfix do a couple of nice 5 year ones (you replace after 5 years).

[Gel]

Fire Blankets are good for TV & PC monitor fires as well as chip pans!!

Extinguishers & Blankets here:

[Guy King]

The message from "Mary Fisher" contains these words:

From Wikipedia...

Dry Powder ("Dry Chemical" in the US)

For classes B and C, a dry powder is used. There are two main dry powder chemistries in use:

• BC powder is either sodium bicarbonate or potassium bicarbonate, finely powdered and propelled by carbon dioxide or nitrogen. Similarly to almost all extinguishing agents the powders acts as a thermal ballast making the flames too cool for the chemical reactions to continue. Some powders also provide a minor chemical inhibition, although this effect is relatively weak. These powders thus provide rapid knockdown of flame fronts, but may not keep the fire suppressed. Consequently, they are often used in conjunction with foam for attacking large class B fires. BC extinguishers are often kept in small vehicles since they provide good knockdown of a rapidly flaring class B fire, from a small package.

BC Powder has a slight saponification effect on cooking oils & fats due to its alkalinity & sometimes used to be specified for kitchens prior to the invention of Wet Chemical extinguishers. Where an extremely fast knockdown is required potassium bicarbonate (Purple K) extinguishers are used. A particular blend also containing urea (Monnex) decrepitates upon exposure to heat increasing the surface area of the powder particles and providing very rapid knockdown.

• ABC powder is monoammonium phosphate and/or ammonium sulfate. As well as suppressing the flame in the air, it also melts at a low temperature to form a layer of slag which excludes the gas and heat transfer at the fuel surface. For this reason it can also be effective against class A fires. ABC powder is usually the best agent for fires involving multiple classes. However it is less effective against three-dimensional class A fires, or those with a complex or porous structure. Foams or water are better in those cases.

Both types of powders can also be used on electrical fires, but provide a significant cleanup and corrosion problem that is likely to make the electrical equipment unsalvageable.

[Nick]

My cheapskate fire extinguisher (works fine when fat catches fire under a stove element):

Buy a tin of baking soda (sodium bicarbonate) from your supermarket. Drill about 30 holes in the lid. Put some aluminium foil over the top to keep it from getting greasy. Put the tin by your stove. If anything catches fire, rip off the foil and shake the bicarb on the fire. The heat decomposes the bicarb into solid sodium carbonate, carbon dioxide gas, and water. The carbon dioxide puts out the fire. Then clean up the mess. You needed to clean out all the fat under the element anyway!

[Andy Dingley]

Ammonium phosphate (if it feels caustic). Be careful with this, it _is_ nasty on skin exposure. Eye exposure is casualty time.

Sodium bicarbonate used to be used, but it's only found in the very smallest (and useless) extinguishers these days. Make sure you buy one labelled as ABC - if it's just labelled BC then it's sodium bicarbonate.

Potassium bicarbonate is used for metal fires (class D) but it doesn't work. It's sometimes reccomended for class B too (liquids), but if these are likely, then get an AFFF (foam) extinguisher and do it properly.

The ubiquitous Lidl 2kg / £10, 6kg for £14 2kg is the minimum size that's useful.

Fire is safer than hot carbon tet in a confined space. Keep this useful and hard-to-obtain solvent for better purposes (or give it to me for safe disposal)

[Frank Erskine]

I've still got a Pyrene extincteur somewhere in the shed.

[<me9]

I remember that one. Is it still the same shed?

[nightjar]

...

If you buy dry powder again, make sure that you get one marked as containing ABC powder. That will work on solids (class A), liquids (class B) and gasses (Class C). However, as you discovered they are messy and they also have limited powers of penetration into enclosed spaces. My preferrence these days is for an AFFF (aqueous film forming foam) spray extinguisher. The spray versions are particularly efficient and AFFF will handle both class A and class B fires - few people need to tackle Class C fires in the home.

Colin Bignell

[meow2222]

There was a carbon tet extinguisher where I volunteered once, I made a mental note to avoid it if at all possbile in case of fire. I wonder what nut thought it was a good idea and why. A volatile toxic rapidly absorbed narcotic, which would burn to form assorted toxins, in the middle of a fire... how helpful.

The place still had its 1942 wiring and electrical equipment, but I think the extinguisher was a lot more modern. At least I suppose it would have more chance of being effective the old pointy cone low pressure ones.... yes, same organisation.

So why were CCl4 extinguishers used?

NT

[Dave Fawthrop]

|On 1 Mar, | "Mary Fisher" wrote: | |> Today we had the need to use the small dry powder fire extinguisher from |> the caravan - not in the caravan. |> |> I'd like to know what the powder is - it feels like extremely fine sand but |> it's also caustic and obviously has some kind of salt in it - I |> accidentally licked my finger. | |I was under the impression it was sodium bicarbonate.

plus something to stop it getting damp and caking |> I know that we're going to have to replace it even though we only used it |> for a two second burst (it did the job splendidly, if messily) but does |> anyone have any authoritative recommendations, please? | |The fire peeps allowed us to have one instead of a fireblanket when we were |childmnding, but pointed out that they were extremely messy.

You can say that again! I used one on a *tiny* fire as an experiment to see how well they worked. Worked fine, but it took days before we got the powder cleared up, it went everywhere. | |> |> Our larger CO2 extinguisher was out of gas (it hasn't been serviced for |> years so that's not surprising!) | |We used one on a burning TV set once, It put (blew) the fire out but it |re-started as soon as the stuff cleared. | |> and the other one we have employs carbon tetrachloride which wasn't |> suitable for the small conflagration we had. It was in a confined space so |> the resultant phosgene could have been nasty.

IIRC Carbon Tetrachloride ones are now banned.

|You must have had that one since Noah was a lad.__

No since Mary was a girl, which is almost as long ;-)

[Dave Fawthrop]

|Mary Fisher wrote: |> Today we had the need to use the small dry powder fire extinguisher from the |> caravan - not in the caravan. |> |> I'd like to know what the powder is - it feels like extremely fine sand but |> it's also caustic and obviously has some kind of salt in it - I accidentally |> licked my finger. | | |Bicarb. Used because it's cheap, has a high thermal capacity and |relatively low toxicity. | | | |> I know that we're going to have to replace it even though we only used it |> for a two second burst (it did the job splendidly, if messily) but does |> anyone have any authoritative recommendations, please? | |For extinguishers? Screwfix do a couple of nice 5 year ones (you replace |after 5 years).

Lidl ones will last for 10 years.

[Dave Fawthrop]

|Grunff wrote: | |> Mary Fisher wrote: |> |>> Today we had the need to use the small dry powder fire extinguisher |>> from the caravan - not in the caravan. |>>

|>> I'd like to know what the powder is - it feels like extremely fine |>> sand but it's also caustic and obviously has some kind of salt in it - |>> I accidentally licked my finger. |> |> Bicarb. Used because it's cheap, has a high thermal capacity and |> relatively low toxicity. | |My cheapskate fire extinguisher (works fine when fat catches fire |under a stove element): | |Buy a tin of baking soda (sodium bicarbonate) from your |supermarket. Drill about 30 holes in the lid. Put some aluminium |foil over the top to keep it from getting greasy. Put the tin by |your stove. If anything catches fire, rip off the foil and shake |the bicarb on the fire. The heat decomposes the bicarb into solid |sodium carbonate, carbon dioxide gas, and water. The carbon |dioxide puts out the fire. Then clean up the mess. You needed to |clean out all the fat under the element anyway!

Much easier to get a cheapy Lidl one

[Autolycus]

"nightjar .uk.com>"

I'd agree totally with Colin on the recommendation for AFFF. Dry Powder extinguishers were withdrawn from use in a very large fleet of road vehicles a few years ago because of problems with compaction of the powder due to vibration, and replaced with one or two-litre AFFF units. AFFF is, perhaps contrary to expectation given that the "A" stands for aqueous, safe for use on normal electrical equipment. Cartridge-operated (as distinct from stored-pressure) units are rather easier for d-i-y periodic checking.

[Andrew Gabriel]

The one thing it completely destroys is electronic printed circuit boards. The failure is not instant, but happens a few days after exposure. I've worked for a couple of large computer manufacturers, and it's not uncommon to get systems back for repair which have been nearby something on which a dry powder extinguisher was used. Upon inspection, the PCB tracks have all corroded through.

[Sponix]

I wondered what Martin Fry was doing these days. He obviously runs a fire extinguisher factory..

sponix

[Peter Parry]

If you can find an old BCF extinguisher snafffle that - it is the most useful general purpose extinguisher. However they have now been banned from sale because of their ozone depleting potential.

By far and away the best alternative is Aqueous Film Forming Foam (AFFF). It isn't particularly messy and can be used on any domestic fire. AFFF is water based (usually between 93-99% water) with temperature stable surfactant additives which promote wetting and foaming. It is effective on most domestic/garage fires and if you only want one extinguisher or type is the best to chose. Not only is it effective at knocking down fires its film forming property helps keep them out and delays or prevents burnback

Dry powder has a number of disadvantages - the first is that the damage it causes is often greater than that caused by a very small fire. It is positively dangerous on hot fat as it blows the burning fat all over the place and on other fires, although it knocks them down quickly, it doesn't prevent burnback so if the fire isn't completely out it simply re-ignites straight away. CO2 also shares that disadvantage and is of limited use in most domestic fires.

[Mary Fisher]

Ah - that's possible. I'll test it. I said 'caustic' because that's what Spouse said when he got some in a cut in his finger. He said ouch or oh dear or heckythump or some such. I didn't mean that it was a chemical base.

They're right! We have blankets too but they were inappropriate. Water was too.

LOL! It would have worked in the confined space of our fire.

It was Spouse's father's, he was in the National Fire Service during the war and was paranoid but I don't think the extinguisher came from those days! There's a date on it but I've forgotten it.

Mary

[Mary Fisher]

Thanks!

I'll have a look. He got a catalogue the other day. And last week. And last month ...

Mary