CO2 portable extinguishers and NFPA10

[DavidCR]

I work for an electric power and telecomunications company.
For most of our facilities there are electric equipment pannels every where and I consider that following NFPA 10 most of our facilities involve A:C fires.

People here have a strong preference with CO2 extinguishers since they are very reluctant to withstand with the possibility of cleaning the mess related with dry chemical of A:B:C extinguishers on expensive electric equipment.

So for years we have used CO2 portable extinguishers, are listed for B:C fires only.

I have to make a proposal for an hydroelectric power plant, I want to follow NFPA 10 and I´m thinking that in general ABC dry chemical extinguishers are the recomended choice. Mostly A:C fires with some possibility of B fires.

People here want to use CO2 extinguishers anyway, but I have told them that the ABC dry chemical extinguishers is a more effective choice and its initial cost is cheaper, also that CO2 may damage equipment due to thermal shock.

We also have B:C fires (dealing with some areas where lubricatng oil is present)but our questions deals more with the general areas.

I want to more clear in some aspects, so my questions are:

a). Is it a good choice to provide ABC dry chemical and also CO2 extinguishers?. Is it a good practice, or it can be a confusion or a contradiction with the NFPA10.

b) Is there some points that can lead to a decision of using CO2 instead of ABC considering the risk of electric cabinets of a power plant.

c) Are water mist extinguishers a good choice as an alternative for our case?.

d) Am I correct asuming that an electric cabinet is an A:C risk considering the type of extinguisher to be used?

We also have other fire protection equipment, automatic sprinklers and nozzles, a good detection system, trained personnel, and others mentioned by NFPA 851 for hydroelectric power plants.

An external AHJ or insurance people have not helped much in this case, they just want to have the extinguishers following NFPA10 and they dont care much of the type of extinguisher used.

 

[stookeyfpe]

Based on what is described:

A) CO2 is probably the extinguisher of choice for your hazards.

b) The big concern with ABC extinguishers in your environment is the cleanup and possible corrosive effects of the fire extinguishing agent. An the agent in a ABC extinguisher is monoammonium sulphate. Even after extensive cleaning, the moisture in the air can react with the agent to cause localized corrosion.

c) I've recommended the use of these extinguishers in the semiconductor manufacturing environment. These would also work well in your environment.

d) Your hazard is a Class A and C fire hazard.

The one area I would examine more closely is any generator sets used as standby power. If your managing switch/data centers my experience is that these facilities have large volumes of diesel fuel. In this case you clearly have a Class B fire hazard.

 

[DavidCR]

Thanks stookey, just to clarify some of your comments about my quesion a):

I´m aware of the mess and corrosion potencial risk on using dry ABC chemical I´m thinking of it because of the A hazard protection requirement for electric cabinets.

What I´ve seen is that people here install ABC dry in order to satisfy the A hazard protection requirement and beside it you find a CO2 unit in order to give a choice of having a clean agent. But this is a little tricky to me: "in case of a little fire emergency is you think that you can avoid the mess you can take with you the CO2, but if you want to be more effective and you don´t care about the mess you use the ABC dry." ????

So do you think that it would be OK to use only CO2 even if CO2 is not listed for class A hazards?.

c)Do you know if water mist extinguishers have a C hazard limitation on a certain voltage or current?. We deal with high voltages so I´m not sure if water mist will be OK for that. But if I´ve no problem with that, water mist seems to be the best choice.

About the diesel generator, yes we have one, it is in an independent room and in this case we don´t have an inportant concern about cleaning up the mess, so we can use there ABC dry or CO2, our doubt is with the other general areas with electric cabinets.

By the way Stookey, thanks for your valuable comments I´ve found in many of the posts in this NFPA forum.

 

[stookeyfpe]

CO2 won't work on a Class A fire hazard. Your best bet may be a Class A & C extinguisher. I've recommended the installation of the following extinguisher in semiconductor fabrication facilities:

http://www.amerex-fire.com/water_mist.html

The Class C rating is a test of the agent's conductivity. The indicated extinguisher does have a UL listing so it should not pose an electrical shock hazard.

 

[Slowzuki]

In power plants I have spec'd ABC's based on size/travel distance requirements and the reduction allowance for hose stations. We then placed CO2 extinguishers at electrical / computer room entrances and around other specific electrical hazards.

If you have a Class A fire in a piece of switchgear, you will be replacing it likely so contamination isn't a huge issue.

I do like hose stations in generating stations to be electrical type ie no solid stream option. Nowadays though fewer and fewer clients expect their employees to fight fires due to liability concerns. Most discourage employees from using the hose stations and even extinguishers unless they have had training.

Having worked as a fitters assistant during a summer job years ago, I'd guess about half the guys would be interested in fighting a fire, the other half would say I don't get paid a cent for that and walk out, maybe letting someone know lol.

 

[fireguy519345]

I own a small fire equipment company. We try not to give people a choice when using fire extinguishers, there is too much stress to allow an untrained person to make an informed decision as to the best extinguisher to use. However in this situation I would use the Amerex water mist to cover the A class ordinary flammables. The water mist is UL listed for energized electrical circuits. Just remember the water mist requires recharging each year w/DI water. Deionized water has no minerals in suspension, and therefore will not conduct electricity. Failure to use DI water will void the UL listing, besides giving someone a surprise. Using water pm energized electrical circuits does make some people nervous, so you may want to contact Amerex at

http://amerex-fire.com/

and talk to someone on the sales staff or engineering department. Amerex also has warehouse/sales offices located in various areas. Halon or Halotron is also an alternative. You will find a single Halon or Halotron will cost more than the combination of water mist and CO2 extinguishers. I would recommend signs located at each extinguisher noting the uses of the extinguishers. CO2 will control A class fires, with certain limitations. Those limitations do prevent a UL listing on A class fires.

Douglas Hicks
General Fire Equipment Co of Eastern Oregon, Inc