Flash points of fuels
Paul H. Brown (phbrown@CAPACCESS.ORG)
Wed, 22 Oct 1997 08:36:17 -0400
Some information comparing safety aspects of propane (C3H8) and gasoline
as stove fuels.
Paul H. Brown, KD4UPD
I used to be an Antelope, WB 82-66
Scout Roundtable Commissioner, Assistant District Commissioner, Pack CC
George Washington District, National Capital Area Council, BSA
From: Blaine Brown <firstname.lastname@example.org>
There are several things that make propane more dangerous than gasoline (or
The NFPA flammability index for propane is 4 (highly flammable gas), for
gasoline it's 3 (flash point below 100 F). Handbook values for FP are N.A.
for C3H8 and ~-40 C for gasoline. I guess the NA means that, since it's a
gas, it's flammable at any reasonable temperature. Boiling point for C3H8
is -45 C.
Also, as you know, propane must be pressurized, making its use and storage
more difficult, and leaks more dangerous. A few years ago, we bought a
second propane tank for our gas grill to have on-hand when the first tank
ran low. It had a leaky valve - I had to "flare" the contents of it all
during the night just to empty the thing! Luckily, the store refunded the
price and the price of the propane I had to flare.
The big danger for propane is the vapor density - it settles in low places
(unlike natural gas) and therefore doesn't disperse. There are building
codes that (I think) prevent its use in basements. About 20 years ago
(while I was in southern France) there was a huge accident in a Spanish
campground (Barcelona area?) when a propane tank leaked and filled the
campground with propane vapor. One spark was all that was necessary.
Flammability limits are about the same for propane and gasoline, can't
remember them now, but the range is about 2-12 volume percent. Of course,
H2 is the most dangerous, with limits of 4-74%.
>I am pretty sure our Council doesn't have any such of a policy at
>present. We use liquid fuel all over the place. A Silver Beaver,
>currently serving with the Great Scout, once told me that bans like
>this existed for boys under a certain age. i.e. adults and older boys
>were allowed to start them but the younger boys were not supposed to.
>My guess, no long possible to confirm, was that adult supervision was
>a problem and probably a nasty incident occurred.
>After watching for awhile some poor starting practices when the tanks
>leaked at each seam and having had a fire ball on both my hands from
>a lighter as a boy I certainly can see reasons for concern.
>A few suggestions, possibly the one or two chemists on the list can
>add some more current and more accurate information.
>You are looking for a few things. Each chemical used in industry has
>what engineers call an MSDS (Material Safety Data Sheet). It is a
>federal requirement that the manufacturer give a pile of information
>to assist industries in protection of their employees. On this sheet
>should be listed pertinent safety information. Probably if we all did
>everything perfectly each Council should have these sheets and a set
>of Chemical Protection Guidelines.
>Each explosive chemical has what they call a Flash Point, a Fire Point,
>and I believe it is called an AutoIgnition Temperature. Household
>alcohol (isopropanol) has a room temp flash point at if I remember of
>about 68F. A Flash Point is just that when a spark is brought close
>and the chemical flashes. A Fire Point is when you supply an ignition
>source remove the source and the fire burns. An autoignition temp-
>erature is when it will start by itself. Wood, well at least one type,
>I believe has an AutoIgnition Temp of around 450F. Another factor for
>some chemicals is an oxygen/chemical concentration that will actually
>cause an explosion when an ignition source is brought close.
>Wham! Bang!! goes that Gasoline Engine or Natural Gas when the
>concentration is just right (about 4-6% if I remember). Anyway that's
>my recollections on the subject w/o getting out my handbooks.
>For your situation I recommend one of a few local sources to assist
>you in understanding and selling a safe situation from the chemical
>fire and explosion side of the subject.
>1>Industrial Fire Extinguishing Companies
>Companies hire these people to install proper protections
>2>Local Natural Gas Utility
>Some are chartered by their state to supply the public information
>3>Local OSHA Office
>(They won't know but they can point you to a source.
>4>The Best Fire Department you have
>and that Pyro Guy that everyone admires for his knowledge
>5>Local chapter of the American Society of Chemical Engineers
>6>Local chapter of Industrial Safety and Environmental Health Engineers
>Anyway good luck, keep safety first, and please rsvp.
Terry Howerton Sakima Group, Inc. SCOUTER Magazine Kansas City