This little gem (freon) is going to pay off big time real soon. I bought R-22 for about $35/30# container a few year back. Just paid $460.00 for same container last week. I would guesstimate 80% or more residential units still use R-22.
The NEW refrigerant R-410 is not interchaneable with R-22. To Use in an older system requires a flush and recharge with new gas. New gas operates about 100 psig HIGHER than older gas. Gonna be a lot of hot residents, real soon.