Standards Development

Scope

This part of IEC 60079 is concerned with the classification of areas where flammable gas or vapour hazards may could arise and may then be used as a basis to support the proper design, selection, installation construction, operation and maintenance of equipment for use in hazardous areas.

It is intended to be applied where there may could 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 3.7.3 and 4.74.5);

d)      rooms used for medical purposes;

e)      domestic premises;

f)       where a hazard may could 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 could 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 could 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 flammability of 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 could 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.For example, larger distances may apply for naked open flames when considering hot work permits.This document does not take into account the consequences of ignition of an explosive gas atmosphere except where a zone is so small that if ignition did occur it would have negligible consequences (see 3.3.8 and 4.6.24.4.2).