۴-۴ Metal Towers and Tanks. Metal towers and tanks constructed so as to receive a stroke of lightning without damage shall require only bonding to ground terminals as required in Chapter 3, except as provided in Chapter 6.

۶-۲ Fundamental Principles of Protection. Protection of these structures and their contents from lightning damage shall require adherence to the following principles:
(a) Liquids that can give off flammable vapors shall be stored in essentially gastight structures.
(b) Openings where flammable concentrations of vapor or gas can escape to the atmosphere shall be closed or otherwise protected against the entrance of flame.
(c) Structures and all appurtenances (e.g., gauge hatches, vent valves) shall be maintained in good operating condition.
(d) Flammable air-vapor mixtures shall be prevented, to the greatest possible extent, from accumulating outside of such structures.
(e) Potential spark gaps between metallic conductors shall be avoided at points where flammable vapors can escape or accumulate.