Fighting summer heat.

Any refrigerants other than the small cans you can get from the auto parts store for your vehicle.
Some refrigerants require further certification such as amonia systems due to it being lethal.
Fun fact....propane is an excellent refrigerant.....so is water R718....but is generally mixed with a brine solution

 

Yeah you are referring to the small cans of r134 in the auto parts store. Buying a 30 pound jug without your refrigerant card won't happen in a place of business

 

I have seen jugs of R410 for sale on ebay

 

Yes however you have to have certification to use it. Eventually someone will get hammered for it

 

I had someone who would be able to charge a walking freezer once (th guy didn't have certification, just knows how to do it), but couldn't find place who would sell me freon without proof of certification, so I don't know how that person could get R410.

 

"Perfect for Mini-Split (Ductless) Systems & Topping Off Your Unit Without Spending A Lot Of Money."

This is from one of eBay listings. Is that really legal to sell it in that way?

 

There is a gray area. For example you can buy a package unit for your house and have it delivered. That's fine. Don't get caught trying to install it because it requires you to make duct work to put it in.
Now you can change a fan motor, contactor, capacitor.....anything electrical but don't get caught trying to change a expansion valve because it requires refrigerant recovery.....that requires CFC certification

 

He might have had contacts with a company that processes used appliances. Before they scrap appliances, they drain refrigerant from old fridges and freezers.

That refrigerant needs to go somewhere, and there's really no way to audit how much they should have.

EDIT. Sorry to necro. Was redirected here from a modern thread.