The production, emission, or escape of smoke within the city of a degree of darkness equal to or greater than number two on the Ringelmann's Scale, from any fire or fires, whether such fires are active, burning, banked, or in a state of rest, or whether the smoke is permitted to escape through a stack, flue, chimney, or from an open space, except for a period or periods aggregating six minutes in any one hour during which time the firebox or fireboxes are being cleaned out, or a new fire or fires are built therein, is hereby declared a nuisance. (Ord. 462-1949, passed 3-3-49) Penalty, see § 94.99