Ozone is a constituent of the natural ambient atmosphere and occurs dependent on weather and environment in concentrations that can trigger airway inflammation. Oxygen concentrators are employed in oxygen long-term therapy and produce in the room air a mixture of concentrated oxygen and residual gases of unknown ozone concentration. Hence, we studied the ozone concentration of the air supplied by the oxygen concentrator, both under normal conditions in the room air and with increased ozone concentration of the air in the room. Both under room air conditions and under increased ozone concentrations of up to 12 ppm in the surrounding air the residual gas mixture of the air produced by the oxygen concentrator did not contain any ozone concentration beyond 0.005 ppm. This prompts us to suggest that the oxygen concentrators examined by use are ozone eliminators rather than ozone concentrators.