Are there any refrigerants that are legal and safe to vent to the atmosphere? I have a dehumidifier manufactured in 2010 that I'm disassembling to gather electronics and other components to start a useful tinkering collection.
How exactly is your question and the statement that followed related?
Co2 requires high pressure around 900 to 1000psi.
You can get some stuff called 12a or 22a from auto supply stores which works near the same pressure as traditional r12/r134a. I think the stuff is just some mixture of propane butane etc.
ammonia, r 600, technically anything thats a hfc refrigerant shouldn't kill the ozone...
maybe don't stand around an ammonia system while you vent it... make sure to smoke while venting an r 600 system...
they make a tool that looks like a vice grip that has a needle that stabs into the tubing, it's got a port to screw a hose to on the other side. also they make ports that you can screw onto it.