(a) The inside dimensions of enclosure shall be as small as practical, but not to interfere with the quick removal of the extinguisher.

(b) Walls shall be tightly constructed of wood, not less than ½ inch thick; the inside of the cabinet to be lined with ½ inch wallboard, or its equivalent, so arranged as to leave a ½ inch air space between the inside and outside walls.

(c) Door shall be of double construction, closing into a rabbet, hinged and held closed with a spring latch.

(d) Near the bottom of the door, and at point opposite to the incandescent lamp, the door shall be double glazed (size of glass not larger than 4 by 7 inches), with double strength glass, and airspace of ½ inch maintained between the glazing. The outer glass should be clear red (or blue) so that the lamp used for heating purposes may be readily observed, and also the location of the extinguisher indicated.

(e) At a point about four inches up from the bottom, there shall be provided four ¼ inch iron rods set into the sides of the cabinet, and arranged to carry the extinguisher.

(f) Under these rods, on the back of the cabinet, shall be mounted a three-inch conduit box and receptacle. All wiring shall be done in accordance with the National Electrical Code, by means of flexible or rigid conduit, or approved reinforced portable cord.

(g) An incandescent lamp of sufficient capacity (not less than 50 watts) to keep the temperature in cabinet above 40° F., but to in excess of 90° F., shall be continuously burned or thermostatically energized during cold weather.

(h) Electric heaters listed by Underwriters' Laboratories, Inc., may be used under the conditions specified.