Re: Tesla Coil Firehazards (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Fri, 31 Aug 2007 06:38:10 -0700
From: Jim Lux <jimlux@xxxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: Tesla Coil Firehazards (fwd)

At 08:46 PM 8/30/2007, you wrote:

>---------- Forwarded message ----------
>Date: Thu, 30 Aug 2007 20:49:25 -0700
>From: Frank <fxrays@xxxxxxxxxx>
>To: Tesla list <tesla@xxxxxxxxxx>
>Subject: Re: Tesla Coil Firehazards (fwd)
>
>Usually a C class extinguisher is CO2 which is only effective in an
>enclosed space where there is no air supply so it can smother a fire.


Not so.  I've used CO2 extinguishers (which, btw, are rated BC) in 
the great outdoors to good effect on such things as burning flammable 
liquids or things like burning electical stuff.  They're also often 
used on stage sets in connection with pyro effects.

Smothering is only one mechanism by which CO2 works, the other 
mechanism by which it works is cooling the fuel below the ignition 
temperature. Yes, after you've blasted with the CO2, the thing might 
be smoldering, and can certainly reignite.


>The space has to be small or the gas is disbursed and it is not
>effective. If you are in the space, you get smothered too!

An interesting question pops up.  If you have a standard 10 or 20 
pound CO2 bottle in your garage, and you vent it all (e.g. by firing 
that extinguisher), will you suffocate?

CO2 expands about 550:1, and, assuming that in the liquid state it's 
about like water.  A 20 pound bottle (a 10BC extinguisher) would be 
about 1/3 cubic foot of liquid, or, after expansion, say 200 cubic 
feet.  A garage might be 20x20x8 feet or 3200 cubic feet.  So the 
oxygen concentration will be reduced to 21%*3000/3200 = 19.7%, which 
will still support life.

Now... having that 20 lb bottle in your 8x8x8 ft dorm room, already 
packed with air displacing junk (tesla coil parts, bed, books, 
minirefrigerator with beer in the corner, etc.) might be a bit 
dicier.  Open the darn window.


>  A hand
>held extinguisher for C fires will not be too effective in a garage 
>or outside.
>CO2 is typically used for confined spaces that the ventilation can be
>shut down and there is a bank of large cylinders that is discharged.
>The number of cylinders is calculated for the space volume. Common on
>ships for the switchgear and engine rooms.