Fresh-air exchange helps prevent unwanted ripening and the accumulation of odors, and ensures longer shelf life for many perishables. It is particularly useful for commodities that produce high levels of ethylene, like tomatoes and apples.
The amount of fresh air needed depends on the tolerance of the commodity to low levels of oxygen and high levels of carbon dioxide and ethylene, as well as the rate at which the commodity respires and produces ethylene.
Fresh-air exchange systems can be set at different levels and are measured in cubic feet per minute (cfm) and in cubic meters per hour (cmh).
