installed, equipment specified in 500.7(K)(1), (K)(2), or (K)(3) shall be permitted.

The type of detection equipment, its listing, installation location(s), alarm and shutdown criteria, and calibration frequency shall be documented when combustible gas detectors are used as a protection technique.
FPN No. 1: For further information, see ANSI/ISA-
12.13.01-2003 (IEC 61779-1 through -5 Mod), Perfor-

mance Requirements, Combustible Gas Detectors, and

ANSI/UL 2075, Gas and Vapor Detectors and Sensors.

FPN No. 2: For further information, see ANSI/API RP
500, Recommended Practice for Classification of Locations

for Electrical Installations at Petroleum Facilities Classi-

fied as Class I, Division I or Division 2.

FPN No. 3: For further information, see ANSI/ISA-RP
12.13.02-2003 (IEC 61779-6 Mod), Installation, Opera-

tion, and Maintenance of Combustible Gas Detection

Instruments.

(1) Inadequate Ventilation. In a Class I, Division 1 loca- tion that is so classified due to inadequate ventilation, electrical equipment suitable for Class I, Division 2 locations shall be permitted. Combustible gas detection equipment shall be listed for Class I, Division 1, for the appropriate material group, and for the detection of the specific gas or vapor to be encountered.

(2) Interior of a Building. In a building located in, or with an opening into, a Class I, Division 2 location where the interior does not contain a source of flammable gas or vapor, electrical equipment for unclassified locations shall be permitted. Combustible gas detection equipment shall be listed for Class I, Division 1 or Class I, Division 2, for the appropriate material group, and for the detection of the specific gas or vapor to be encountered.

(3) Interior of a Control Panel. In the interior of a control panel containing instrumentation utilizing or measuring flammable liquids, gases, or vapors, electrical equipment suitable for Class I, Division 2 locations shall be permitted. Combustible gas detection equipment shall be listed for Class I, Division 1, for the appropriate material group, and for the detection of the specific gas or vapor to be encountered.

(L) Other Protection Techniques. Other protection techniques used in equipment identified for use in hazardous (classified) locations.

500.8 Equipment Articles 500 through 504 require equipment construction and installation that ensure safe performance under conditions of proper use and maintenance.

FPN No. 1: It is important that inspection authorities and users exercise more than ordinary care with regard to installation and maintenance.
FPN No. 2: Since there is no consistent relationship between explosion properties and ignition temperature, the two are independent requirements.
FPN No. 3: Low ambient conditions require special con- sideration. Explosionproof or dust-ignitionproof equipment may not be suitable for use at temperatures lower than -25°C (-13°F) unless they are identified for low-temperature service. However, at low ambient temperatures, flammable
concentrations of vapors may not exist in a location classified as Class I, Division 1 at normal ambient temperature.

(A) Suitability. Suitability of identified equipment shall be determined by one of the following:

(1) Equipment listing or labeling

(2) Evidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluation

(3) Evidence acceptable to the authority having jurisdiction such as a