Chapter 4, Ventilation Air Supply, is hereby amended by adding the following section:

406.0 Screened Openings. Inlets and outlets of ventilation air supply systems shall be equipped with screen, grills or louvers to prevent the introduction of foreign materials and to deny vermin admission to the system. Screens, grills or louvers shall not pass an object larger than a 1/4-inch-diameter (6.4 mm) sphere.

Exception: An outside-air inlet serving a nonresidential portion of a building may be covered with screen having openings larger than 1/4 inch, but in no case larger than 1 inch.