600790-000100-0000101 Scope
This part of IEC 60079 is concerned with the classification of areas where flammable gas or vapour hazards may arise and may then be used as a basis to support the proper design, construction, operation and maintenance of equipment for use in hazardous areas.
Modification of Clause 1, first paragraph and additional paragraph as follows: Replace "part of IEC 60079" with "document".
Electrical installations in areas where flammable liquids or gases are produced, processed, stored or otherwise handled can be suitably designed if the locations of potential sources of release and accumulation are clearly defined. Once a location has been classified, requirements for electrical equipment and associated wiring should be determined from applicable publications. Applicable publications may include NFPA 70 (NEC) or API RP 14FZ. Reference Section 2 for other possible applicable publications.
It is intended to be applied where there may be an ignition hazard due to the presence of flammable gas or vapour, mixed with air, but it does not apply to:
a) mines susceptible to firedamp;
b) the processing and manufacture of explosives;
c) catastrophic failures or rare malfunctions which are beyond the concept of normality dealt with in this standard (see 7.3 and 5);
d) rooms used for medical purposes;
e) domestic premises;
f) where a hazard may arise due to the presence of combustible dusts or combustible flyings but the principles may be used in assessment of a hybrid mixture (refer also to IEC 60079-10-2).
NOTE Additional guidance on hybrid mixtures is provided in Annex I.
Flammable mists may form or be present at the same time as flammable vapour. In such case the strict application of the details in this document may not be appropriate. Flammable mists may also form when liquids not considered to be a hazard due to the high flash point are released under pressure. In these cases the classifications and details given in this document do not apply. Information on flammable mists is provided in Annex G.
For the purpose of this document, an area is a three-dimensional region or space.
Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar) and 20 °C (293 K), provided that the variations have a negligible effect on the explosion properties of the flammable substances.
In any site, irrespective of size, there may be numerous sources of ignition apart from those associated with equipment. Appropriate precautions will be necessary to ensure safety in this context. This standard is applicable with judgement for other ignition sources but in some applications other safeguards may also need to be considered. E.g. larger distances may apply for naked flames when considering hot work permits.
This document does not take into account the consequences of ignition of an explosive atmosphere except where a zone is so small that if ignition did occur it would have negligible consequences (see 3.8 and 2).
Modification of Clause 1, seventh paragraph to add the following as last sentence: Explosive atmospheres are identified by the National Electrical Code®, NFPA 70 as hazardous (classified) locations.
Modification of Clause 1 to add the following paragraphs: With respect to the application of this standard in the US, the classification of a plant/plants are to be recognized as the classification of a facility/facilities.
Where references are made to IEC and ISO standards, the referenced requirements found in these standards apply as modified by any applicable US National Differences for the standard (see Clause 2).