501.13 Conductor Insulation, Class I, Divisions 1 and 2.
Where condensed vapors or liquids may collect on, or come in contact with, the insulation on conductors, such insulation shall be of a type identified for use under such conditions; or the insulation shall be protected by a sheath of lead or by other approved means.
Nylon-jacketed conductors, such as Type THWN, that are suitable for use where exposed to gasoline have gained widespread acceptance because of their ease in handling and application as well as for economic reasons.
Underwriters Laboratories Inc.'s Electrical Construction Materials Directory states the following under ?Wires, Thermoplastic-Insulated.?
THWN ? wire that is suitable for exposure to mineral oil, and to liquid gasoline and gasoline vapors at ordinary ambient temperature, is marked ?Gasoline and Oil Resistant I? if suitable for exposure to mineral oil at 60?C or ?Gasoline and Oil Resistant II? if the compound is suitable for exposure to mineral oil at 75?C. Gasoline-resistant wire has been tested at 23?C when immersed in gasoline. It is considered inherently resistant to gasoline vapors within the limits of the temperature rating of the wire type.
