No person shall cause, suffer or allow to be emitted into the open air from any fuel-burning equipment during normal operation, smoke, the shade or density of which is equal to, or darker than the shade or density of #2 of the Ringelmann Chart, except for one minute in any 30-minute period, during which the smoke may be greater than #2 of the Ringelmann Chart, and except as hereinafter provided.
(Ord. 2673, approved 8-6-1957)