§ 93.13  DENSE SMOKE AND ODOR.
   (A)   It shall be unlawful to cause or permit the emission of dense smoke or odor from any fire, chimney, engine, oil burner or other agency in the city so as to cause annoyance or discomfort to the public.
   (B)   For the purpose of testing and grading the density of smoke, the Ringleman Smoke Chart, as published and used by the United States Geological Survey, shall be and is hereby adopted as a standard for the grading, and smoke shall be and is hereby defined and declared to be dense smoke when it is of a degree of density of number three as classified by that chart or of any greater degree for more than six minutes in any one hour, whether the period of time is consecutive or not.
   (C)   Provided further, that, fly ash or dust shall not exceed 83 pounds per 1,000 pounds of gas of which not to exceed five pounds per 1,000 pounds shall be of a size as to be retained in a 32.5 mesh United Standard.
(1980 Code, § 21.413)  Penalty, see § 93.99