Each building in a fireworks plant shall be constructed as provided in this section. This subsection applies to a building that is constructed or improved after July 1, 1970, or to which an addition is made after July 1, 1970. The following buildings in a fireworks plant shall have exterior walls and roofs that are constructed of noncombustible material and shall be constructed to be frangible: a finishing and assembling building; a press building; and a mixing building. A building in a fireworks plant may not contain a basement or exceed one story. The interior wall surfaces and ceilings of a building in a fireworks plant shall: be smooth, free from cracks and crevices, and fire resistant; and contain a minimum number of horizontal ledges on which dust may accumulate. A floor or work surface in a building in a fireworks plant may not have cracks or crevices in which explosives may lodge. A wall joint or opening for wiring or plumbing in a building in a fireworks plant shall be sealed to prevent entry of dust. A mixing building or press building in a fireworks plant shall contain conductive flooring that is properly grounded. A building in a fireworks plant shall be heated by: steam; indirectly radiating hot air; hot water; or any other means approved by the State Fire Prevention Commission. All electric wiring in a fireworks plant shall be permanent and installed in approved conduits. All electrical service shall comply with applicable electrical codes. Temporary or loose electric wiring or extension lights may not be used except: during repair operations while using approved temporary extensions; and after the area has been cleared of all explosive composition and washed of dust. Each fireworks plant shall have a master switch that: is located at the point where electric current enters the fireworks plant; and on being opened, immediately cuts off all electric current to the fireworks plant. Other than in a warehouse, an open knife switch may not be used inside a building of a fireworks plant. Artificial lighting in a fireworks plant shall be provided by electric, vapor-proof, keyless lamps. Except as provided in paragraph (2) of this subsection, each building shall contain: at least two exits for each work area; and at least two exits from the building. Each small building with a designated capacity of one individual may have only one exit. Each exit shall be at least 30 inches wide. Exits shall be located: so that the path of travel from the work area is unobstructed; and at opposite ends of the work area. An exit door shall: open outward; remain unlocked during the hours that the work area or building is occupied; and remain unobstructed.