Where conditions exist which are found to make smoking a hazard in any area on piers, wharves, industrial plants, or in open spaces where combustible materials are stored or handled, the Chief shall direct the owner or occupant, in writing, to post “NO SMOKING” signs on each building, structure, room, or place in which smoking shall be prohibited. The Chief shall designate specific safe locations, if necessary, in any place in which smoking may be permitted. Such signs shall be in contrasting color, with lettering not less than 3 inches in height.