I was assuming that all of the people on the Diesel Forum were smart enough to not smoke ... period.... since they already have a higher COPD exposure risk just from being around Diesels in the first place...

I would like to think this as well !!
All our cars have the cig lighter removed.
It is surprising when some one asks if you mind if they smoke, you say you do & they get upset.

Any propane leak is most likely to pool near the floor. The tiny spark from the brake peddle switch might do the trick when you put your foot on it.

In 1971 I had an Army buddy ask if I minded him smoking in the car... I said Yes, he proceeded to start to light up.. I stopped the car and offered to let him out.. in the middle of a Texas summer and a long way from anything on a large Army base...before the invention of cell phones..... LOL
He decided to stay in the car... but was Surprised that I actually meant ' No '....after me saying ' No '....

Propane pooling... spark....Talk about ' blowing smoke up your pant leg '

Guess when I run out of propane for my torch I might fill it with r134.

If I do, i'll take a pic for you.

All refrigerant are hydrocarbons.
All hydrocarbons burn, and can explode.

Gasoline, or diesel fuel leaking from your car in an accident is far more
likely to combust, than refrigerant from your ac system.

Try turning your torch on all the way before you light it.
It is very hard to light, and will usually blow a cigarette lighter out,
instead of igniting.

It takes a very precise mix of fuel and air for a substance to ignite.
That's why vehicles have carburators and injectors.
And torches have mixing nozzle.

Tell that to those who in the past have used a BCF fire extinguisher !!!

Ammonia is a very commonly used refrigerant as well. No carbon in it !!!

Hydrocarbons can be used as refrigerants, Organo-halogens like freons do a far better job.

Key Concepts UNNECESSARY and easily AVOIDABLE risks
 

How old are you ?
You are mixing and matching your ' examples' to fit your needs.... not based on reality and legitimate safety concerns.

As already mentioned.... gas and fuel in cars is protected as best they can within cost factors..
BUT changing to propane and putting it at the front of the vehicle is clearly a very different and UNNECESSARY potential danger.

Lets take your gas carb example ....with manual choke... all it takes is to fully choke it.... maxing out the density of the gas-air ratio... open the throttle fully....crank the engine ... and take the choke all the way off.... what happens is that it AUTOMATICALLY starts at the point where the two ratios cross at whatever the engine is needing.. .which can vary depending on lots of conditions... but it offers all the combos automatically..... so if fuel to air ratio is what is keeping the engine from starting....that will be provided by that method.
In and accident with random sparks happening due to friction... releasing propane in the area has a huge potential for hitting that correct fuel to air ratio.... and if you are pinned in the vehicle... you are then subject to a potentially fatal and UNNECESSARY risk even if the accident was totally survivable otherwise...

Everyone should see ' The Great Waldo Pepper' with Robert Redford....

Great Movie... Of course nothing to do with propane but very illustrative of secondary events being a disaster.

Still, a pound of Propane? Not that much in the scheme of things. Now the Hindenberg (H2, I know)!?! Point clearly made; however...

' Pound of Propane' ... the bigger picture includes ( in addition to unnecessary risk ) the fact that propane may not provide the oil miscibility needed to lube our R4 compressors....as they do not have a sump... and I do not know how efficient it is compared to R12 or R134a.....and the fact that finding a shop which will work on it... very doubtful...( I always worry about being caught hundreds of miles from home on a trip and needing service ).

As to the Hindenberg... on PBS ' History Detectives' or Nova there was a really great investigation which concluded that the problem was not the H2 but that the skin was made of very inappropriate material...

Notice reference to propane here...
http://www.seas.ucla.edu/hsseas/releases/blimp.htm

" "Actually, its great buoyancy and extremely high diffusivity in air make for a very rapid dispersal before ignition can take place," Van Vorst further noted. "Gasoline, on the other hand, with its heavier-than-air vapor, simply accumulates until a flammable mixture is formed and ignites." In fact, he said, hydrogen is even "safer than propane, and is on a par with natural gas.""

Seriously, there's likely more propane in a can of hairspray than it takes to charge an a/c. Propane is so efficient that it only requires about 1/3 the charge compared to R12 or R22 while typically outperforming either. It is also miscible in all common refrigerant oils. It's high side pressure will run higher but can be brought down with a slight addition of Butane.

I'd still be a lot more worried about travelling at high velocities with 15+ gallons of gasoline on board.

Do you have any cans of hairspray tied to the front of your car ?
You are in the Diesel Forum.... we are not carrying gasoline in our cars....
Can you speak with authority about the oil miscibility question ?

I don't have a link, if that's what you're asking. I read it somewhere longer ago than I can remember and experience has confirmed it. Liquid propane is a really good solvent. I think you would be hard pressed to find a lubricating oil it wouldn't dissolve into.

Are you using propane in your car AC ?
if yes, what pressures are you seeing ?
What oil did you use ?

I currently have it in a stationary system that was originally R22. It runs around 45/325 in hot weather. Was gonna shoot a little butane into it but the performance was so superior to the R22 that I decided not to mess with it. Using ester oil in that system. FWIW, with R22 it would run constant for hours on end. WIth propane it will cycle off the thermostat in 10 minutes.

It will run similar pressures in a mobile system. Since there is variance in compressor speed and airflow in mobile systems, it can spike higher but it's hard to set a rule how much.

No one is complaining about the idea of using it in a stationary system...

If your only objection is the risk of some catastrophic explosion in the very unlikey event of system compromise and ignition.... I'm not terribly convinced. I've seen a you-tube of a propane charged car blow a hose on the dyno and ignite it. It lit and blew flame like a large aggressive torch.... whoosh, not kaboom. Is there risk, yeah maybe to a small extent, but that risk isn't the car exploding into a fireball from a ding in the condensor.