Mysterious Shock Received When Operating Fire Extinguisher...

see post #55

My apologies 34point5... you had it, I apparently didn't pay enough attention when reading. Thanks.

Not a problem CI, well, actually, it's a common enough 'problem' all over.

& I do think it is good that Guest brought up Navy training as a possible source of "known problems", behind what I always just took as "proper extinguisher & smoke technique".

I am very interested to find out if this is a "reason behind", that has been "lost", prior to my training, so now absent from my instructing, and obviously that of other instructors on the thread, so the OP's training program.

It would be great if someone could post the relevant part of the Navy instructors manual.

As you expected, still no reply from NFPA. Will keep you informed or even resend the email to a specific address.

I did find these esp shoes. They may be something that people could wear during dry seasons to dissipate the static. It is kind of like wearing the tin foil on your feet instead of your head. FYI

Well it's sort of on topic as to the severity of the shock.

You will note the 'shoe earth straps' are a megohm - which acts as a earth in the static buildup sense, but acts as a current limiter, keeping a person fairly safe, in terms of not being 'fully earthed', so far as, say contact with mains power.

It is one of the interesting things about rubber and rubber alloys, that they become conductive at high voltages.

Or gumboots are not protection against lighting. And wearing earth straps would be a good way the get the best shock possible from a big static source.

I.e. 'rubber soled' work boots are no protection if it's static, but possibly quite good protection if it was 'mains leakage' - (depending on their condition and composition and structure and moisture and/or sweat. ^{_{The latter two, possibly high if She is about.}})

I am not sure that they will help or not. They may even make the problem worse for all I know.

It really depends on how the discharge took place. If it was a "flash-over" over the shoes, then they would probably help.....

Is this the source of the saying "I wouldn't want to be in your shoes!"

When I pointed out the special anti static shoe tapes it was for Ky, who has a problem with static buildup on his person for no apparent reason. Which was why I placed it as being Off Topic....

I know it's been mentioned, but in a quick scroll through the posts, I didn't see this detail/theory thrown out: if the worker did indeed have on gloves, he was insulated from the fire extinguisher, and if a charge was building up on in, it would have to exceed the insulation threshold of the gloves to discharge. Perhaps this is part of the reason there was a large enough discharge event on his second, longer blast, to knock him over? Bare hands on the extinguisher would be a completely different scenario, and I don't see any real discussion about that part of the setup. My $.02 worth.

Tom D.

Hello Jon,

I dont know the answer but am taking a guess.

Any substance leaving containment under pressure cools to a certain degree. Perhaps such cooling was great enougth to allow a moisture build up along the stream path to allow electricity to pass back to the operator.

Cheers

Peter

This just came in from the NFPA:

Kevin,

It is my understanding that ABC extinguishers typically do not create a sufficient static charge for this to be a concern. Typically, static discharge is a problem only with carbon dioxide extinguishers. It is more likely that the "shock" was generated by another source of energy.

I recommend that you contact an extinguisher manufacturer for further clarification.

I hope this satisfies your inquiry. If you need additional assistance, please do not hesitate to contact NFPA's Technical Advisory Service.

Sincerely,

Barry D. Chase

Fire Protection Engineer

NFPA

I guess that's in line with my searches (#67), but it's not a result I expected.

It's not the response I expected either. I reread the OP with this information in mind and thought about this...

He gave the fire a short blast of dry chem from about 6 feet away and felt a tingle in his hands.

Come to think of it... I can't remember any single time I would describe a static electricity discharge as a tingle. It's always sharp and quick. Wouldn't tingling be more of a sustained current?

We checked the grounding in the area and found that everything was properly grounded. There was an existing ground fault in another motor about 100 yards away that had been existing for some time.

Given a known ground fault (and in light of the NFPA info), I would move that to the top of my suspect list.

Well, All,

As is maybe normal with mysteries, there is a real simple answer. It is called getting the facts straight right off the get-go.

Bottom line: The fire extinguisher used was NOT a dry chem; it was a CO2 unit.

The water was muddied by the fact that someone hit the motor (after the first response from the CO2 extinguisher) with a dry chem extinguisher. It took quite a bit of talking to find that little tidbit out!

The CO2 unit was hand-held, off the ground while being discharged, so the user experienced the static charge buildup and discharge while using the extinguisher.

I found some research papers on the web from the 1980's that discussed the voltage buildup; it can go as high as 50kV within about two seconds or so after the CO2 discharge is started. The energy is not high, so the static discharge is not dangerous to the operator unless their involuntary motions cause potential injury.

The funny thing is that the researcher tried various ways to reduce the static buildup and came up with a couple of ways to knock it down to almost nothing. But the extinguisher we used, which is a "Flag" trade name, doesn't look like it has any of the static mitigation measures. And when I phoned the outfit that owns the "Flag" name, I got someone who must have been a boot camp Sergeant: "You modern pussies who can't stand some static electricity! @#%$^&%$. " No a lot of interest from this guy.

So, we know how the shock happened. We are looking at reviewing our fire extinguisher training to accommodate this issue.

Thanks, All, for your interest and input! It has been an interesting thread!

Jon.

Good luck.

I'd be "reflagging" my extinguishers with another brand from the sound of their response.

Happy Holidays!

Just to say it again... (see 34point5's post #55 for more)... the extinguishers should always be placed on the ground prior to discharge (for your training purposes).

Glad to see the mystery solved. It has been interesting.

I asked Mr. Flag about that, pointing out that the US Military trains both CO2 and Dry Chem to be set down before using. His response was "I was in the military, too, and I wasn't trained that way. After all, they are portable, use them as portable! And thats how I train people, blah, blah." A perfect example of a human 1-way valve. All out, no in.

Jon.

Well I'm glad that sorted it self out to a "known issue"- though not to you or your guys, unfortunately.

I'm mightily Disappointed that your suppliers "trainer" is such an ignorant A-hole (classic case of "loss of passing on WHY" in training)

What you might like to do is contact the local fire service and ask them if they will run a short course, or let your guys attend their next extinguisher training day.

Mostly this comes under fire awareness education/PR and is part of the service (free) - not to sure about 'all parts of all countries' though.

Meanwhile - come in 'under the smoke', and as you said above, should not see anyone flung into anything.

And thanks for being concerned enough to bring this here - and staying through the "process"

Bringing in the local volunteer fire department to help with this training is certainly on our agenda.

I'll also suggest that we modify our purchasing of CO2 extinguishers by asking the suppliers come up with static electricity data, now that we know that the static generation is controllable.

By the way, for those that are interested, the research report is:

"Electrostatic Effects with Portable CO2 Fire Extinguishers"

By G.J. Butterworth and P.D. Dowling,

Published in the Journal of Electrostatics, 11 (1981) pp 43-55.

It is available for purchase off the 'net at about $40 US. It makes for interesting reading and, like I mentioned before, offers a solution to bring the electrostatic production down to nearly nothing when operating a fire extinguisher. And as they are not patented solutions, they are fair game to anyone. There are some fascinating photos in the report of electrostatic discharges taking place in a specially-made clear plastic CO2 horn. Looks like a mini electrical storm.

That is why I am floored that the one supplier I contacted was so weird about static discharges. The extinguisher in question was built 18 YEARS AFTER this technical report was published, so it should have been mainstream in the extinguisher industry by then. But then, why should I be surprised? I'm sure military people were still buying swords 18 years after the machine gun was developed... :>(

Jon.

, check on who trains who - as you might find the 'townies' train the volunteers in such as extinguishers and BA (breathing apparatus).

Good Point! There is a "paid", real live fire department not far away and they will likely have the training HP that we need. And probably to the level of detail we need.

Jon.

It's probably 'free' either way - but 'good form' is to make a donation - these guys are always scratching for new equipment. Often just the 'small bean' stuff.

Also - I don't know about Canada - but a lot of places have a "fire warden" or "fire marshal" qualification, for corporate employees.

They learn basic response skills, OH&S, evacuation, and first aid, etcetera. This then gives you someone on hand to keep the training/awareness current with the other guys, and train new guys.

Generally they get all the updates rattling around the fire fighting organizations. And they see to things like dates, position of types, proper signage, that hoses, hydrants whatever works. And obviously the right person will bring some order to response if something happens - despite the 'preventive measures' they've produce.

Picking such a person is something generally done during some sort of live fire training. As you can never 'guess' how people react to a real fire. Whichever organisation you pick to train your guys, have a quiet word up front with them, on who they might pick.

Otherwise you are generally looking for a 'floating shop floor' person, with some leadership experience or potential. Not necessarily an existing gang leader or shift boss.

You want one per shift minimum. It might cost you a bit in time off and maybe course fees, but that will possibly come off your insurance premium.

I would still like to know; has it be determined if the shocked party was or was not wearing gloves? Seems like it would be good to know which would cause the least operator "discomfort" when using a CO2 extinguisher, should the situation arise again.

Tom D.

Tom,

Yes, they were wearing gloves. It was too cold out to do anything "ungloved".

I think the least operator discomfort would be to do what you can to ground the extinguisher out before actually pulling the trigger. This would be putting it on the ground, against a piece of wood or metal that is connected to the ground or similiar. Anything to give the static charge an easy way off the fire extinguisher. Since the charge can get to a significantly high voltage, unless one was wearing electricians gloves rated to 50kV, you WILL eventually get a static electricity shock off of the extinguisher unless it is grounded.

Jon.

Thanks for letting us know. Interesting, Ky.

I don't know about pussies but I remember getting shock (rooster) and then I learned to swear like a boot camp sergeant.

Good detective work and it is nice to see a resolution.

Cheers