Date: Tue, 30 Apr 1996 08:44:09 -0700
Sender: Vanagon Mailing List <vanagon@vanagon.com>
From: Mark Howser <mchowser@initco.net>
Subject: RE: Clean Fire Extinguishers
Ken,
Unfortunately, you won't find a fire extinguisher that effectively stops =
the fire and remains clean at the same time. Fire is the result of a =
chain reaction involving an increase in temperature, availability of =
fuel and an adequate supply of oxygen for combustion purposes.
To extiguish a fire, interrupt the essential elements of fire. Doing =
one of these will extinguish the flame.
1. Reduce the temp.
2. Remove the fuel.
3. Exclude O2.
4. Stop the Unihibited Chain Reaction (Note: This method is effective =
on gas =20
and liquid fuels b/c they must flame to burn. This is where your =
Halon fire extiguisher comes in. The Halon (hologenated =
hydrocarbon) replaces the O2 which causes the fire to stop flaming. =
However, smoldering fires are not easily extinguished, b/c the moment =
the Halon is shut off, air again has access to the smoldering fuel and =
reignites, continuing to burn.
Types of Extinguishers:
Class A: Ordinary Combustibles (wood, paper, rubber, plastic)
Class B: Flammable Liquids (liquids, greases, gases)
Class C: Electrical Equipment (live electrical equipment)
Class D: Combustible Metals (magnesium, titanium, and other "iums")
Class A exting. are rated from 1A to 40A depending on their size. For a =
1A rating 1 1/4 gallons of water are required. A 2A rating requires 2 =
1/2 gallons of water. (see the trend?)
A dry chemical extiguisher with a rating of 10A is equivalent to five 2 =
1/2 gallon water extinguishers.
Class B extinguishers are rated from 1B to 640B. A complicated UL =
rating system best described by "...the 60B extiguisher will =
effectively extinguish a sixty square foot fire when used by a non =
expert...."
Class C refers to whether the extiguishing agent conducts electricity. =
You wouldn't want to spray a flaming engine with a class A fire =
extinguisher unless you wanted to chance shock or electrocution.
Class D--you aren't going to effectively stop the spread of burning =
metals with any portable extinguisher. Call the FD, EPA and any other =
toxic spill agency that comes to mind.
A fire extinguisher is rated as follows.
4A 20B:C
This extinguisher should extinguish a Class A fire that is four times =
larger than a class 1A fire, extinguish approx. 20 sq/ft of class B fire =
and is also safe to use on energized equipment.
Good luck,
Mark
80 Westy
East Glacier Volunteer Fire Department