Careful !!!Potter Loki is right, but you also need to remember that the way some markers use air, some is usually retained in the reg/valve system. I have an Azodin and when I de-gas with the on/off I put on it, there is still enough air for one shot held in the valve. so after I de-gas I switch off and reverse my hopper a couple of turns, point in a safe direction and let one shot go to fully de-gas and make safe.