11.   Five hundred million years after bacteria spawned hemoglobin, certain algae began producing oxygen, which slowly built up in the atmosphere, Stamler said.

12.   In response to the malfunction, the crew turned off the spinning gyrodynes that steer the panels and also shut down the device that produces breathing oxygen from wastewater.

13.   Once ignited, the candles produce oxygen in a chemical reaction.

14.   Oxygen generators use chemical reactions to produce oxygen.

15.   Oxygen generators are designed to produce oxygen when a passenger tugs on the oxygen hose that drops down after an airplane loses cabin pressure.

16.   Plants appeared and produced more oxygen.

17.   The chemical reaction that produces the oxygen also generates heat, and in normal use, the generators are well insulated to prevent surrounding material from catching fire.

18.   The canisters, carefully position in airplanes, are used to produce oxygen in case of an emergency.

19.   The generators are used to produce oxygen for passenger emergency oxygen systems.

20.   The objective was a device to produce oxygen photochemically from water.