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 ordnance facilities than inhabited building distances, as defined in
DOD-STD-6055.9. When failure of the lines and stations will not cause serious
hardships, both the towers or poles supporting the lines and the stations may
be located at public traffic route distances.
4.7.3
Clearance Calculation. Line clearance distance calculations shall
be based on airblast over pressure only. Fragment distances will not be used.
4.8
Flagpoles and Chimneys. Provide grounding at the bases of metal
chimneys or flagpoles at the lowest points in accordance with NFPA 78.
Provide protection for other chimneys and flagpoles in accordance with NFPA
78.
4.9
Towers and Antennas. Provide grounding at the bases of metallic
towers or at the lowest points in accordance with NFPA 78. At least two
columns should be connected to an adequate ground by No. 2/0 AWG (67.4 mm)
copper cable. Provide the same grounding for metallic watch/surveillance
tower structures. Structures adjacent to metallic towers and within their
zone of protection do not require primary protection, but all metal frames,
ventilators, doors, and window frames shall be bonded together and adequately
grounded. Provide antenna lead-ins with spark gap protection connected to
ground adjacent to supporting structure of antennas.
4.10
Aircraft and Aircraft Hangars. Provide aircraft and aircraft
hangars in accordance with NFPA 78. Grounding receptacles shall be located in
accordance with DM-21.1, Airfield Geometric Design, and DM-21.9, Skid
Resistant Runway Surface.
4.11
Ordinary Buildings. Provide protection in accordance with NFPA 78.
Health care facilities are included under ordinary buildings, except
protection for flammable liquids and gases shall apply as appropriate. Where
air terminals are located on flat roofs, either near mechanical equipment or
in areas traversed by maintenance personnel, special consideration must be
given to preventing injury from tripping over air terminal points, such as
installing longer or elevated air terminals.
4.12
Obstruction Lights. Provide air terminals 1 ft (0.3048 m) above the
top of the obstruction lights. Provide surge arrestors connected to the
lighting circuit conductors and bonded to the lightning protection system.
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