ventilating the room with outdoor air to prevent, owing to respiration of the fruit during ripening , (i) accumulation of carbon dioxide (CO 2 ) to >10 000 ppm, which (a) inhibits fruit ripening and (b) poses a human health hazard, and (ii) depletion of oxygen (O 2 ) to <10%, as O 2 is required for ripening. maintaining a temperature of 15-25 • C.