ANSI/ISA-RP12.13.02 (IEC 61779-6 Mod) gives guidance on the selection@ installation@ use@ and maintenance of electrically operated group II apparatus for the detection and measurement of flammable gases complying with the requirements of ANSI/ISA-12.13.01 (IEC 61779-1 through 5 Mod). It is a compilation of practical knowledge to assist the user@ and applies to apparatus@ instruments and systems that indicate the presence of a flammable or potentially explosive mixture of gas or vapour with air by using an electrical signal from a gas sensor to produce a meter reading@ to activate a visual or audible pre-set alarm or other device@ or any combination of these. NOTE ?? When in classified areas@ the apparatus should be so installed and used that it is not capable of itself igniting a flammable gas-air mixture. It should therefore comply with the requirements of ANSI/NFPA 70@ Articles 500-505. For the purpose of this document flammable gases shall include flammable vapours. This document applies only to group II apparatus intended for use in industrial and commercial safety applications@ involving areas classified in accordance with ANSI/NFPA 70@ Articles 500-505. For the purpose of this doment@ apparatus includes a) fixed apparatus; b) transportable apparatus; and c) portable apparatus. This document is not intended to cover the following: a) Apparatus intended only for the detection of non-flammable toxic gases b) Apparatus of laboratory or scientific type intended only for analysis or measurement purposes c) Apparatus intended for underground mining applications d) Apparatus intended for applications in explosives processing and manufacture e) Apparatus intended only for process control applications f) Apparatus intended for the detection of a potentially flammable atmosphere resulting from dust or mist in air