Oxygen should not flow except when the patient inhales. The patient breathes in the Oxygen and exhales a normal breathe. The concentration of oxygen from the patients exhaled breathe will be no greater than a person breathing unassisted.
not all concentrators use a breath regulator,
many are free flow
and yes it would be hard for them to build up a concentration..inside the whole rv
but yes there is excess oxygen around the nose piece
please be careful with the hose, a snag, break or worn spot can cause a fire
don't drag the hose/tubing around electric heaters or any form of heat