Thread: Fire Extinguisher Fun

Last week.

At work, start of every shift At home I have 2 vaporizing liquid extinguishers. These are the ones that replaced the ozone depleting BCF (Bromo,chloro,Difluromethane) which are OK to use but a little expensive to buy. Vaporising liquid are the go in the shed as it does not create a mess that costs more to clean up than the fire! That white powder makes a lovely grinding paste! Also, vaporising liquid extinguishers are "reasonably" easy to test as you can tell with a shake how much liquid is there which is a backup to just relying on the gauge. As it requires pressure to store it in the liquid phase, you know it must be charged. WRT Dry powder, once they are discharged even the smallest amount of powder, they will go "flat" very quickly since the valve cannot seat properly as it has powder in it, within hours the charge of dry nitrogen will escape and you will end up with an extinguisher with near on 9Kg of powder but no pressure. While the gauge should reflect this, if the extinguisher is old it's not unusual for the needle to stick and still show "full" in the green zone. Best way to check is to look in the nozzle or give it a tap. It should be clean and have no sign of powder, if it has then it's been used. Of course nothing beat water for A class fires.... as long as any electrical hazard has been isolated. Cheers, Simon

Ray, I shake them real well after knocking with a dead blow hammer all over. I was told that is necessary with dry powder extinguishers once a year, to prevent the powder from clumping. I found that some of my extinguishers do loose pressure over the years. Normally these get recharged with Nitogen gas. I have no Nitrogen cylinder at home, but I have Argon that I use for the TIG welder. So I made an adapter that on one end connects to the TIG regulator outlet, on the other ends fits the pressurizing nipple on the fire extinguisher. With a needle valve in between to control the charging. Here a pic of my contraption:
Extinguisher_Charger.jpg

Argon is an inert gas, so it is perfectly suitable to charge a fire extinguisher. Nitrogen or CO2 are much cheaper gases, but for the small quantities to charge a 9kg fire extinguisher the price of the gas does not matter. And I have Argon in my workhop, so using it is much more convenient for me than hiring a Nitrogen cylinder or - god forbid - paying someone to have the extinguisher maintained, refilled, recharged and tested and tagged. Before someone is crying wolf, these are not fire extinguishers that I am required to have and maintain by law. I own them solely for my own peace of mind.

I was born with an in built fire extinguisher..

Originally Posted by .RC.

I was born with an in built fire extinguisher..

Not suitable for electrical fires.

Hi Ray,
This is a very timely reminder. We are just starting harvest and spent most of yesterday fighting a large fire started by a hot bearing in a header, which set fire to the crop. So about 100 men, two fire bombing planes and a day off harvesting later the fire is out.
Will be double checking the two fire extinguishers (one water,one dry powder) on the header and the dry powder ones in each truck today!

Mark

I would have to see what class rating sticker it on it...

About 5 years before I retired, a small fridge sized chiller unit (a refrigerated cooler and pump that pumps cooling water through an analytical machine) caught fire inside one of our clean labs at 5am on a Sunday morning. The chiller unit overheated and the plastic housing around the pump caught fire. A student doing the night shift in another laboratory on the other side of the corridor (there are internal windows on the corridor walls in most labs) spotted the flames and called security.

The security office arrived in less than a minute. The fire flames were less than 25 cm high and visibility was excellent. Because the lab was a clean air lab, the sooty smoke from the burnt plastic was continually being captured by the 24, 1.2 x 0.6 x 0.3 m HEPA filters in the lab celing. The fire could have been easily smothered with a fire blanket but there was none available so the security officer looked for a fire extinguisher but did not spot the CO2 unit inside the lab. Instead he grabbed a large powder fire extinguisher from outside the lab and dumped the entire contents onto the fire.

To cut a long story short the final outcome was the lab was totally out of action for 4 months and not fully back into action for another 2 years. All the HEPA filter units had to be replaced due to smoke and powder contamination, one of the million dollar European analytical instruments had to be replaced and that has to be specially ordered and thats what took two years. We also lost an outstanding lab manager due to frustration of getting this sorted out. We received considerable compensation for all this but as usual it did not cover all the expenses.

The big problem for us was the powder (siliconized mono ammonium phosphate) in the fire extinguishers, which penetrates into fine nooks and cranies so a clean up at the level to our requirements was going to be impossible. There were two large analytical machines in the lab. One was far enough away from the fire and powder to be adequately protected by the HEPA filters but the other one was a near new machine right next to the fire and its own cooling fans drew in both smoke from the fire and powder. Another problem with the powder is that it eventually reacts with water vapour to make phosphoric acid which really messes with the sensitive electronics. If these powder extinguisher are used on planes they are not usually permitted to fly again

Despite all this the insurance company did not want to pay out ( there were good and complex reasons that I won't go into here) and initially pursued a cleanup attempt. The insurance company spent big $$ performing a cleanup. They set up a plastic tent around the machine and a team of 4 people in clean room suits spent over two weeks painstakingly removing every electronic board and repeatedly washing the boards in a range of solvent, but we were still not convinced and decided not to accept the cleaned up machine. After the attempted clean up we wrapped the machine in glad wrap (so it did not contaminate the lab again) and months later when it was removed there was a halo of fine extinguisher dust on the floor that had fallen out of the supposedly cleaned machine.

Later we discovered that even if a fire blanket has been used it is possible that the analytical instrument would still not have been OK as some soot from the plastic fire had also been drawn inside the machine. This soot contains HCl which is worse than the ammonium Phosphate. The real issue was the location of the Chiller - It should have been located in an enclosure OUTSIDE the lab as originally requested by me when it was first installed, but I was overridden by a bureaucrat who said it would spoil the outside look of the building to use an enclosure. Despite this the new chiller is still inside the lab.

Now those labs are set up with clearly visible fire blankets and Sapphire MRI extinguishers that cost around $1500 a pop. These use non-magnetic stainless steel containers so they can be used near large magnets which are present in those labs. (In MRI labs where very powerful magnets are used the magnets can drag a conventional steel extinguisher out of an operators hands and fly across the room and serially injure or kill anyone in the way) These extinguishers are AE rated and contain materials that leave no residue on sensitive electronics.

Hi Bob,

That's an interesting story. Thanks for sharing. It does not surprise me though and I dare say this will have happened at many, many other places that contain sensitive equipment in environmentally controlled rooms. I am rather surprised though that such a room(s) are not installed with either an automatic halon dump system (very difficult to get dispensation for unless you are in the aviation industry) or a CO2 system. There are also other products now that produce less thermal shock than CO2 such as Inogen (spelling?) which is a nitrogen/argon mix. I personally don't understand what person in their right mind would even consider installing a dry powder extinguisher anywhere NEAR such a laboratory. Like I said earlier, the clean up bill can end up being 100 times worse than the damage bill from the fire. I personally wouldn't even have a 1Kg dry powder even in the house. The contents of a 0.9Kg dry powder is enough to coat every horizontal surface in an average 20 sq home if all the doors are open at the time of discharge. 12 months after the (small) fire and the insurance company has settled the damage bill, you will see things starting to fail and need major repairs. Motors in washing machines, fridges, computers, dishwashers, TV's & home entertainment systems will all have a fine powder nicely settled every little nook and cranny. Then, with the moisture in the air (worse if you have evaporative cooling) starts to get absorbed by the powder it's game over!

I have seen the results of people who have used a small dry powder on a fat fire. These are good hearted people who thought they were doing the right thing by purchasing an extinguisher and then using it in their time of need but really should have just used a fire blanket, which can be used over and over again. Or always have a lid near the fry pan when using it.

Edit: On a side note Bob, I'm surprised the fire was permitted to develop past the incipient stage. Surely smoke detectors would have been installed or even a VESDA system. Such systems would have detected the fire long before visible flames were present and don't require human senses for detection, in which case it's usually way too late. If that person was not there or did not notice, you would have possibly lost the entire lab.

Simon

bloke comes and checks and tags mine twice a year ( at great expence i might add ). it has to be done or i get in the poo from council and insurance company .

johno

Originally Posted by texx

bloke comes and checks and tags mine twice a year ( at great expence i might add ). it has to be done or i get in the poo from council and insurance company .

johno

Yes, it's quite a lucrative industry but they have you by the short and curlies because you need that "tick in the box" to satisfy both local by laws and insurance.

Simon

Edit: On a side note Bob, I'm surprised the fire was permitted to develop past the incipient stage. Surely smoke detectors would have been installed or even a VESDA system. Such systems would have detected the fire long before visible flames were present and don't require human senses for detection, in which case it's usually way too late. If that person was not there or did not notice, you would have possibly lost the entire lab.

Simon

At work we have extensive smoke detection systems everywhere that barrels are stored. These suck air thru special perforated tubes back to a sensor unit. Sometimes the mist from pressure cleaners used to clean the floor set them off. Time to give your ears a break and nick off.

We have fire extinguisher training once a year. In the office area only CO2 extinguishers are provided. I am not sure why we have fire extinguisher training. There is about 5 km square of foam insulation on the site. Everyone I have spoken to says that if a fire breaks out they have no intention of staying around. We have 2 large barrel sheds that are 6 inch foam with metal skin walls and roof. I don't intend hanging around to breath those fumes. Having said all that, there is very little chance of a fire occurring. Too many restrictions and fail safe/protective devices etc.

Dean

Originally Posted by BobL

......Now those labs are set up with clearly visible fire blankets and Sapphire MRI extinguishers that cost around $1500 a pop. These use non-magnetic stainless steel containers so they can be used near large magnets which are present in those labs. (In MRI labs where very powerful magnets are used the magnets can drag a conventional steel extinguisher out of an operators hands and fly across the room and serially injure or kill anyone in the way) These extinguishers are AE rated and contain materials that leave no residue on sensitive electronics.

I is crazy. In new buildings, the laws require there to be sprinklers even in MRI and NMR rooms. The MRI magnet is filled with liquid Helium at -269 degreesC, and sometimes additionally with large amounts of liquid Nitrogen at -196C. There is absolutely nothing that could burn. Yet an expensive mess is to be expected if a sprinkler gets damaged during a Helium fill or suddenly leaks.

Originally Posted by cba_melbourne

There is absolutely nothing that could burn.

You'd be surprised at what is still flammable in a room. Besides, I would expect on such systems that they would have a dry pipe system. The sprinkler plumbing is charged with nitrogen so that in the event of a damaged sprinkler head, initially only nitrogen gas comes out. Workers will then have a pre-set amount of time to investigate and then override the system to prevent an unnecessary discharge from the head. Can't state for sure that is what is installed but they are available. All depends on what the people with the $$$ are prepared to pay when the place is built.

Also, bear in mind that sprinklers are not necessarily designed to extinguish the fire, they are primarily designed to initially inhibit fire spread and extension to give occupants enough time for safe egress until a response from the local fire brigade. The BCA (building Code of Austrailia) is very strict with building of this class as it invariably has occupants who may be non ambulatory. As such they will be venerable in the event of an evacuation. The BCA does not concern itself with the cost or damage to equipment in the event of fire, it's main concern is the safe egress of ALL occupants in the event of an incident. Having said that, there are provisions in the BCA that enable designers to "deem to satisfy" the BCA by other means if they can demonstrate compliance. New technology or installing a different system that still achieves the same level of protection but does not pose the same damage risk to machines can therefore be installed.

Simon