inputting ethylene (C 2 H 4 ) gas to maintain a concentration of 100-150 ppm (though, ethylene exposure schedule varies by fruit) in order to induce ripening. The source of ethylene is typically a compressed gas cylinder or a catalytic converter that produces ethylene from ethanol on-site . Note, excess ethylene levels could promote spoilage and damage the fruit . inputting water (H 2 O) vapor to maintain relative humidity ≥85%, preventing the fruit from losing moisture.