No use shall be permitted in a combining X district which causes, or is found by the board of zoning adjustments to involve:

    A.    The emission of odorous gases or odorous matter in quantities such as to be perceptible at any lot line of the lot or building site upon which the source is situated; or

    B.    The emission of visible gray smoke of a shade or quality darker than No. 1 on the Ringlemann Chart as specified in Circular 7718 of the United States Bureau of Mines, or its equivalent opacity as determined by the Bay Area Pollution Control District, for more than three minutes in any one hour. (Ord. 2002-60 § 1 (part); Prior gen. code § 8-43.1)