Open flames, heating devices and processes employing temperatures capable of igniting the vapors of the flammable liquids used shall be prohibited in buildings, rooms and other confined spaces in which Class I or Class II flammable liquids are used in the open, or in which Class III flammable liquids are used for the purpose of saturating, coating or otherwise treating goods or materials. Artificial lighting shall be by electricity only. Electric devices located within the possible path of vapor travel shall be of a type approved for such locations. Compliance with applicable provisions of the Standards of the National Board of Fire Underwriters known as the “National Electrical Code” shall be deemed prima facie evidence of compliance with this section. Smoking shall be prohibited and suitable signs to that effect shall be displayed.