During the period from June 1 to October 31 every door, window and other outside opening used or required for ventilation purposes serving any building containing habitable rooms, food preparation areas, food service areas, or any areas where products used in food for human consumption are processed, manufactured, packaged or stored, shall be supplied with approved tightly fitting screens of not less than 16 mesh per inch and every swinging door shall have a self-closing device in good working condition.
EXCEPTION: Screen doors shall not be required for out-swinging doors or other types of openings which make screening impractical, provided other approved means, such as air curtains or insect repellent fans are employed.