On Fri, 17 Jul 2015 04:00:13 -0700 (PDT), stryped
wrote:

Thinking about getting house ac unit replaced and using current hvac for my garage/shop. I know nitrogen is typically used in hvac for brazing copper line sets and for pressure testing. Can i use my argon/co2 mig mix for the same?

Could i use helium also purchased from wal mart that is used for ballons? I actually read helium is even better for leak checks.Because the molecules are smaller.
I guess my only concern are if these gasses are "dry" enough.
Helium has more than doubled in price over the last year or so.
Your welding mix will work fine for pressure testing/purging.