Date:         Fri, 10 Nov 2000 12:02:05 -0800
Reply-To:     Bjorn Ratjen <Bjorn@IGLIDE.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Bjorn Ratjen <Bjorn@IGLIDE.NET>
Subject:      fire extinguisher info for vanagons
Content-Type: text/plain; charset="iso-8859-1"

After all this discussion about fir extinguishers, Halon etc. makes me
think that I should re-post my summary from a year or so ago:

Well, let's hear it from a firefighter.

Fire extinguishers have have four classes:
A: wood, paper products, some plastics
B: flammable liquids
C: charged electrical equipment
D: combustible metals

In a vehicle you are concerned mostly with A,B, and D type fires.
Interestingly fire departments use mostly water for extinguishing car fires
unless there is a larger fuel spill (class B, where foam would be used) or
magnesium components such as the transmission housing in a vanagon and type
2 (class D, where special agents or dirt would be used, no water because it
would fuel the fire). A class C fire is reclassified by turning off the
electricity. 

How effective the agent is also depends on the amount that is available. A
trickle of water may produce steam but does little else. A typical car fire
extinguisher will be empty after about 20-40 seconds.

Fire needs four things:
fuel, heat, oxygen, chemical chain reaction

If you take one of these components away you will have no fire.

Examples:
Water takes away temperature but has to be available in sufficient
quantities. A CO2 extinguisher takes away oxygen, but is succeptible to
wind influence. A powder extinguisher also interrupts the access to oxygen
and because reignition can occur easily a coating agent is added which
makes the powder stick to hot surface. The powder in an A,B,C type
extinguisher is very corrosive and difficult to remove from cars once
applied. That's where there is additional damage in the long term through
rust. 
Halon interupts the chemical chain reaction and as a gas is also influenced
by wind and location. Halon however is detrimental to the atmosphere and
can build very toxic components in high heat. That's why it has been mostly
discontinued.

In a car fire the key elements are size of fire and speed of response. It
is really a question of damage control. The small car extinguishers are
usually good to buy some seconds to extricate a person unless you catch the
fire very early. 

By the way cars usually do not explode as seen in the movies. There can be
spontaneous combustion through fuel leaking onto hot engine components. But
that happens usually immediately during an accident and produces first
small then rapidly expanding fires. One exception is the Ford Pinto where
the fuel tank could burst upon rear impact on the differential which
sprayed fuel over the exhaust (genius at work). VWs will generally not
explode (unless sufficient heat is applied to propane tanks in campers and
even they usually vent first).

Vanagons mostly have fires through leaks in their array of fuel lines, like
improper connections to the injectors, or through some camping accessories
or electrical causes.

To extinguish a fire:
Think about safety first (passengers, people, traffic, etc., the gases
coming from a burning vehicle can be extremely toxic)
Think about removing the fuel 
(i.e. disconnect battery in an electrical fire) and things which can burn
(I once removed a burning hose from the auxiliary heater on a 75 Bus to
extinguish the fire).
Think about limiting the spread of the fire and try to remove oxygen 
(i.e. use water, dirt, fire extinguishers, etc. I was at a scene where a
guy successfully extinguished an engine fire in his VW Bug by throwing
roadside dirt into the engine compartment, which meant overcoming some
inhibitions)

A note on use of fire extinguishers think PASS:
At the scene
        Pull the pin
        Aim towards the fire
        Squeeze the handle
        Sweep spray towards base of fire

My suggestion: prevent fires through maintenance and keep a cool head.

regards,

Björn