Bad CO2?

[schwaggs]

My CO2 tank ran out last week and I went to the same welding supply place I always go for replacement tanks (at least 4, 20lb cylinders worth). Ever since replacing the cylinder, I have been having problems with undissolved gas collecting at the top of my CA reactor. As first I though I had a leak that was somehow sucking air into the system but I think I have ruled that out. My only remaining conclusion is that there is excess "air" (or something other than CO2) in this cylinder. If the gas collecting at the top was CO2, it would easily be absorbed into the reactor water as it is recycled through the circulation pump...

Anyone ever have bad CO2 or heard of it before or should I keep looking for an air leak into my reactor?