It shall be unlawful to cause or permit the emission of dense smoke from any fire, chimney, engine, oil burner or any other agency in the City so as to cause annoyance or discomfort to the residents thereof.
For the purpose of testing and grading the density of smoke, the Ringelmann Smoke Chart, as published and used by the United States Geological Survey, shall be and is hereby adopted as a standard for such grading, and smoke shall be and is hereby defined as and declared to be "dense" when it is of a degree of density of number three (3) of said Chart, or greater, for more than six (6) minutes in any one hour, whether such period of time is consecutive or not. (1979 Code Ch. 16, Art. III, §12)