It is probably also illegal for use as and R-12 substitute per the EPA.
Here is the link which shows legal EPA approved substitutes:

http://www.epa.gov/ozone/snap/refrigerants/macssubs.html

Per the EPA:
"May hydrocarbon refrigerants be used to replaceCFC-12, commonly
referred to as "Freon� ," in cars?
  No. It is illegal to use hydrocarbon refrigerants like HC-12a� and
DURACOOL 12a� as substitutes for CFC-12 in automobile or truck air
conditioning under any circumstances"

http://www.epa.gov/ozone/snap/refrigerants/hc-12a.html

Here is an old ABC news report on using flammable refrigerants
http://www.youtube.com/watch?v=ANtAbkKrOuI

Supplied so you may make an informed choice.

Todd
'88 Westy

On 4/12/2012 11:24 AM, Rob wrote:
> The other day on the list we were talking about the contents of an
> air conditioning system, a propane/isobutane mix was mentioned as was
> the un-comfort level of having flammables in that system.
>
> I guess it's all relative.
>
> We are sitting on 15.9 gallons of gasoline with a flash point of -50
> degrees f
> There is 2.5 gallons of propane that is a gas at -44 degrees f right
> behind us (well behind me, I have a westy)
> We have brake fluid in front of us, it's a flammable with a high
> flash point (248 degrees f) but it's still a flammable.
>
> Springtime most places, not AC weather up here yet but I've read it
> is some places, which I guess is why we are talking about AC systems
> & the like.
>
>
>
>
> Rob
>
> becida@comcast.net
> Western Washington State, USA
>