Ventilation may be produced by:
1. A natural ventilating system which is hereby defined as a system, the effectiveness of which depends upon natural atmospheric conditions and upon the operation of windows, transoms and other openings, the operation of which is in control of the person or persons in the room or space which is ventilated.
2. A mechanical ventilating supply system, which is hereby defined as a system for forcing air into a room or space by artificial means combined with the removal of air through windows, skylights, transoms, undercut doors, grilles, shafts, ducts, or other relief openings direct to outside atmosphere except as provided in Table 18-28-403.3.
3. A mechanical ventilating exhaust system, which is hereby defined as a system for removing air from a room or space by artificial means combined with a supply of air through windows, skylights, transoms, grilles, shafts, ducts or other relief openings direct to outside atmosphere except as provided in Table 18-28-403.3.