agreed on the “lying gauge”. that happens**. and should always be considered as a possibility. but -20C and 25C don’t look alike even to the untrained eye
he’s been recovering a collection pot of atmosphere everyday…you’re right, I bet it’s 70% N2
** boss got lucky once upon a time. 30/30 gauge said zero. it had wrapped around. clamp he removed was above his head so it missed him.