separately, Class I, Zone 2 locations shall be permitted to abut, but not overlap, Class I, Division 2 locations. Class I, Zone 0 or Zone 1 locations shall not abut Class I, Division 1 or Division 2 locations.

(C) Reclassification Permitted. A Class I, Division 1 or Division 2 location shall be permitted to be reclassified as a Class I, Zone 0, Zone 1, or Zone 2 location, provided all of the space that is classified because of a single flammable gas or vapor source is reclassified under the requirements of this article.

(D) Solid Obstacles. Flameproof equipment with flanged joints shall not be installed such that the flange openings are closer than the distances shown in Table

505.7(D) to any solid obstacle that is not a part of the equipment (such as steelworks, walls, weather guards, mounting brackets, pipes, or other electrical equipment) unless the equipment is listed for a smaller distance of separation.

Table 505.7(D) Minimum Distance of Obstructions from Flameproof "d" Flange Openings

Minimum Distance

Gas Group mm in.

IIC 40 l 37/64
IIB 30 l 3/i6
IIA 10 "/ M

505.8 Protection Techniques. Acceptable protection techniques for electrical and electronic equipment in hazardous (classified) locations shall be as described in

505.8(A) through (K).
FPN: For additional information, see ANSI/ISA-
60079-0 (12.00.01)-2005, Electrical Apparatus for

Use in Class 1, Zones 0 and 1 Hazardous (Classified) Locations, General Requirements; ANSI/ISA-l2.01.01-1999, Definitions and Information Pertaining to Electrical Apparatus in

Hazardous (Classified) Locations; and ANSI/UL

60079-0, Electrical Apparatus for Explosive Gas

Atmospheres — Part 0: General Requirements.

(A) Flameproof "d". This protection technique shall be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(B) Purged and Pressurized. This protection technique shall be permitted for equipment in those Class I, Zone

1 or Zone 2 locations for which it is identified.

(C) Intrinsic Safety. This protection technique shall be permitted for apparatus and associated apparatus in Class I, Zone 0, Zone 1, or Zone 2 locations for which it is listed.

(D) Type of Protection **n". This protection technique shall be permitted for equipment in Class I, Zone 2 loca- tions. Type of protection "n" is further subdivided into nA, nC, and nR.

FPN: See Table 505.9(C)(2)(4) for the descriptions of subdivisions for type of protection "n".

(E) Oil Immersion "o". This protection technique shall be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(F) Increased Safety "e". This protection technique shall

be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(G) Encapsulation "m". This protection technique shall be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(H) Encapsulation "ma". This protection technique shall be permitted for equipment in Class I, Zone 0, Zone 1, or Zone 2 locations.

(I) Encapsulation '*mb'\ This protection technique shall be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(J) Powder Filling "q'\ This protection technique shall be permitted for equipment in Class I, Zone 1 or Zone 2 locations.

(K) Combustible Gas Detection System.