Ethylene is a colourless, odourless, flammable gas; it is produced by natural processes and is also man-made. In nature, the largest producers of ethylene are plants and plant products (fruits, vegetables and floral products).
Ethylene is produced in plant tissues; it acts like a hormone to trigger ripening and decay processes. Tomatoes, bananas, etc. are sometimes placed in paper bags to speed up ripening processes; the bag traps ethylene that is released by the fruit; the increased ethylene concentration results in faster ripening. Any closed container, truck, trailer, warehouse, even a refrigerator will have a similar effect.
Large quantities of ethylene are produced, stored and used locally in the production of plastic resins (polyethylene). Ethylene is uniquely stored in salt caverns some 700 metres below ground level in the Sarnia area. This storage method reduces risks of release, fire, etc.
Ethylene is a volatile organic compound and so it contributes to ozone formation. The acceptable daily average (35 parts ethylene per billion of air ) is slightly exceeded on occasion in Lambton County. It should be noted that the concentration of ethylene in the bag that is used to ripen fruit will be considerably greater than 35 ppb.