gaseous hydrocarbons as broad class also do not appear to cause any appreciable corrosive damage to Inaterials. Of all the hydrocarbons, only ethylene has adverse effects on plants at known ambient concentrations. The principal effect of ethylene is to inhibit plant growth [48]. Concentrations of ethylene from 0.001 to 0.5ppm have caused damage to sensitive plants including flower droppings and failure of the leaves to open properly. Injury to orchids and to cotton has been demonstrated.