I've had the "electric oxygen alarm" tripped by using CPAP from an on board port. Luckily we no longer have those type of devices, that drain the tank severely. It caused an error that shut off the electric oxygen valve, IMO, it was probably from the condensation. This was a feature in our Horton ambulances. In order for the oxygen to flow, you had to push a button on the control panel. The button opens a valve, that's what the "click" is when it's pushed. If you turn off the mod, or shut the vehicle off, there's a louder click, the valve closing. However, by KKKA1822E standards, if your ambulance has one of these, it also must have a bypass valve. The new SOP for CPAP use, on the remaining Horton, is that this bypass valve has to be open during use. So, even if we lose mod power, o2 will flow. Our new ambulances have no oxygen control, if the tank's on, o2 can flow. The only down side, is it has no electric oxygen level meter.