Approved combustible materials as applied to outdoor signs shall include:
(1) Wood or materials not more combustible than wood;
(2) Combustible plastics which, when tested in accordance with ASTM Standard Method Test for Flammability of Plastics over 0.050 inch in thickness (D635-44) burn no faster than 2.5 inches per minute in .060 inch thickness.
(Prior code § 61-2.6)