Hate to vent refrigerant these days, even R134 costs money. Easy way to recover a can from any system. Pull a vacuum on an empty can, put some heat on it to help pull moisture. Run the vehicle for a while to get it hot as possible under the hood. Put the can in some icewater and hook to the AC system and let the freon in the can. The cold can will condense the refrigerant and lower the pressure pulling in more refrig. Shake the can and you'll hear it hiss as it pulls the gas. Pretty easy to get a full can in about a half hour. That's about $25 worth of R12 for free. And, BTW, if the pressure drops to about 40 psi and holds, you're done, that's all you can pull as the system is about empty.

 

i have done the same thing with R-12. but i use an empty 30 pound cylinder & a 10 gallon plastic bucket.
if you put just alittle bit of water with lots of ice & then pour salt on the ice, you can get it alot colder than with just ice & water alone. when i have done this i normally get better than 80% of the R-12 out. the gage will read around 20~25 PSI once im done. i also use an inline filter to pull the refrigerant through & then turn the filter around when i put the refrigerant back in.

i really wouldn't use a small can like that, you can over fill it very quickly & very easily , once it starts to warm back up it can explode. if it is completely full, it WILL explode & it can do it before it reaches room temperature. even a new can you just bought will explode if it gets too hot, i have seen it happen, its not a pretty sight. if it were to explode while your holding it, you could loose your hand, or even worse, your life.

 

You mean, a BLEVE? That's why recovery cylinders have the 80% fill switch in them. I'd sooner use an old empty cylinder than a disposable can, but as long as you're aware of the risks, no one but the EPA can stop you.