don’t use a shop vac to empty your tube if you’re using hydrocarbons. Works great for CO2. it’s probably not safe to empty your fuge with one either, but I’ll go on record as having performed that trick for months without issue. I’ve used an LEL meter on mine, and the exhaust is kosher. the inside of the vac after you switch it off is not. so either you empty it immediately or you’re risking an explosion on restart.
edit: link to an explosion proof vac system is in above thread.