Highly flammable materials such as cotton batting, straw, dry vines, leaves, trees, artificial flowers or shrubbery and foam plastic materials shall not be used for decorative purposes in show windows or other parts of mercantile and institutional occupancies unless first rendered flameproof. Electric light bulbs in mercantile and institutional occupancies shall not be decorated with paper or other combustible materials unless such materials shall first have been rendered flameproof.