Each building in a fireworks plant shall be equipped as provided in this section. A stove, an exposed flame, or an electric heater may not be used in a fireworks plant, except in a boiler room, machine shop, office building, pump house, or lavatory in which fireworks, fireworks components, or volatile chemicals are prohibited. If a unit heater is located inside a building that could, at any time, contain explosive composition: the heater shall be equipped with an explosion-proof motor; and the switches controlling the motor of the unit heater shall be located outside the building in which the motor is located. An electric motor, fan, open switch, or other device capable of producing an open spark shall be located: outside any building in a fireworks plant that at any time contains explosive composition; and in a manner so that an open spark cannot be introduced into a building in a fireworks plant that, at any time, contains explosive composition. A press or other mechanical device located in a building in a fireworks plant that, at any time, contains explosive composition shall be properly grounded to prevent the accumulation of static electricity.