Roy writes:

When they serviced my old AC unit they used a
partially filled freon container they had to put the old freon in, as
they had to repair a slight leak.

That should have been a recovery tank, not a disposable. E.g.,

http://www.grainger.com/Grainger/pro...mId=1611629984

Very bad practice if they used a disposable to recover used refrigerant
from your unit.