Does that mean if in the event of O2D2 failure you can make the system constant flow?
I use the MH O2D2 kit, and yes, you can plug a constant flow mask/cannula into the adapter (the one attached to the bottle). This would bypass the O2D2 in case of failure.
I got my kit (MH O2D2, bottle etc.) from AFE Oxford. They also do the refills 'while you wait' at £20 a time.
Ian