gas switch leaking o2

If you are talking about the gas on/off switch those frequently fail with either O2 or Air leaking out around the toggle switch. Sometimes the problem is intermittent and sometimes you can make it leak by wiggling the toggle switch.  We, Denova Medical have the part for sale on eBay or you can order direct. Repair takes less then an hour and I recommend to take a picture of the switch before you remove the fittings so you know where they go.