Leaking gas from somewhere. Could me minor leak, do a good inspeciton.
gas cap loose..
Check your fuel cap or gas tank for leaks, or maybe the gas lines.
Could be a leak in the manifold, or a hole in the exhaust, and when you stop the car there is no pressure blowing off the fumes, so it floats up into the car.
Typically this is caused when the fuel is burned uncleanly and the sulfur in gas makes it smell
well, when you turn of your car, it stops firing, which means the spark that ignites the gas in the engine stops.
More than likely a leak in the engine compartment somewhere..Especially if you turn the heat on and can smell you can be sure its coming from the front. If its only when the car is running then its probably along the fuel rail somewhere. If you can smell it just as strong when the car is off then its a line and your car probably does not get good gas mileage. start there or take to a mechanic asap! gas is way to expensive now a days!!
An air conditioner should not smell like smoke when turned on (or when turned off). I would have to suspect that the electrical insulation is burning.
Check your park brake. Did you leave it on?
check the seals at the injectors sometimes they leak for starters
Pay your gas bill
The flame goes out because you turned it off.
Car fresheners are an example of sublimation because the freshener gives off a smell, which is really a gas, without becoming a liquid. (Sublimation is a solid changing directly to a gas with out going through the liquid phase)