This part of IEC 60079-29 gives guidance on, and recommended practice for, the selection, installation, safe use and maintenance of electrically operated group II apparatus intended for use in industrial and commercial safety applications for the detection and measurement of flammable gases complying with the requirements of IEC 60079-29-1.
This Guide 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.
Such apparatus may be used as a means of reducing the risk whenever there is the possibility of a risk to life or property specifically due to the accumulation of a combustible gas-air mixture, by providing such warnings. It may also be used to initiate specific safety precautions (e.g. plant shutdown, evacuation, fire extinguishing procedures).
This Guide is applicable for oxygen measurement for the purpose of inertisation where explosion protection is provided by the exclusion of oxygen instead of measuring the combustible gases or vapours present.
This Guide is applicable to all new permanent installations and, where reasonably practicable, to existing permanent installations. It is also applicable to temporary installations, whether new or existing.
Similarly it is applicable to the safe use of portable or transportable apparatus, irrespective of the age or complexity of such apparatus. Since much modern apparatus of this type also includes oxygen deficiency detection and/or specific toxic gas sensors, some additional guidance is given for these topics.
For the purpose of this Guide, except where specifically stated otherwise, flammable gases shall include flammable vapours.
This Guide applies only to Group II apparatus (i.e. apparatus intended for use in industrial and commercial safety applications, involving areas classified in accordance with IEC 60079-10).
For the purpose of this Guide, apparatus includes
a) fixed apparatus;
b) transportable apparatus; and
c) portable apparatus.
This Guide is not intended to cover, but may provide useful information, for 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 (Group I apparatus);
d) apparatus intended only for process control applications;
e) apparatus intended for applications in explosives processing and manufacture;
f) apparatus intended for the detection of a potentially flammable atmosphere resulting from dust or mist in air;
g) open path apparatus not used for point measurement.