taper of 1 in 16 (y4-in. taper per foot). Conduit and fittings shall be made wrenchtight to prevent sparking when fault current flows through the conduit system, and to ensure the explosionproof or flameproof integrity of the conduit system where applicable. Equipment provided with threaded en tries for field wiring connections shall be installed in accordance with 505.9(E)(1) or (E)(2). Threaded entries into explosionproof or flameproof equipment shall be made up with at least five threads fully engaged.

Exception: For listed explosionproof or flameproof equip- ment, factory threaded NPT entries shall be made up with at least 4'/2 threads fully engaged.

(1) Equipment Provided with Threaded Entries for NPT Threaded Conduit or Fittings. For equipment provided with threaded entries for NPT threaded conduit or fittings, listed conduit fittings or cable fittings shall be used.

FPN: Thread form specifications for NPT threads are located in ANSI/ASME B 1.20.1-1983, Pipe Threads, General Purpose (Inch).

(2) Equipment Provided with Threaded Entries for Metric Threaded Conduit or Fittings. For equipment with metric threaded entries, such entries shall be identified as being metric, or listed adapters to permit connection to conduit or NPT-threaded fittings shall be provided with the equipment. Adapters shall be used for connection to conduit or NPT-threaded fittings.

Listed cable fittings that have metric threads shall be permitted to be used.
FPN: Threading specifications for metric threaded entries are located in ISO 965/1-1980, Metric Screw Threads; and ISO 965/3-1980, Metric Screw Threads.

(F) Fiber Optic Cable Assembly. Where a fiber optic cable assembly contains conductors that are capable of carrying current, the fiber optic cable assembly shall be installed in accordance with 505.15 and 505.16, as applicable.

505.15 Wiring Methods. Wiring methods shall maintain the integrity of protection techniques and shall comply with 505.15(A) through (C).

(A) Class I, Zone 0. In Class I, Zone 0 locations, only intrinsically safe wiring methods in accordance with Article 504 shall be permitted.
FPN: Article 504 only includes protection technique "ia."

(B) Class I, Zone 1.

(1) General. In Class I, Zone 1 locations, the wiring methods in (B)(1)(a) through (B)(1)(f) shall be permitted.

(a) All wiring methods permitted by 505.15(A).

(b) In industrial establishments with restricted

public access, where the conditions of maintenance and
supervision ensure that only qualified persons service
the installation, and where the cable is not subject to
physical damage, Type MC-HL cable listed for use in
Class I, Zone 1 or Division 1 locations, with a
gas/vaportight continuous corrugated metallic sheath,
an overall jacket of suitable polymeric material, a
separate equipment grounding conductors) in
accordance with 250.122, and provided with
termination fittings listed for the application.
FPN: See 330.12 for restrictions on use of Type MC cable.
(c) In industrial establishments with restricted
public access, where the conditions of maintenance and
supervision ensure that only qualified persons service
the installation, and where the cable is not subject to
physical damage, Type ITC-HL cable, listed for use in
Class I, Zone 1 or Division 1 locations, with a
gas/vaportight continuous corrugated metallic sheath,
an overall jacket of suitable polymeric material and
provided with