1 This Standard provides guidance for the classification of hazardous areas according to the existence of, or likelihood of the existence of, an explosive gas/air mixture.
NOTE - Areas classified as Zones 0, 1 or 2 in accordance with this Standard are sometimes referred to as Class I areas.
2 It applies to open and enclosed areas, in all above-ground situations, where there may be a risk due to the presence of flammable gas or vapour mixed with air under normal atmospheric conditions (see Note 1).
3 This Standard does not apply to:(a) Areas inwards from the mouth of underground workings, including coal mines, which are subject to the provisions of the Coal Mining Act 1979 or the Mining Act 1971 or in any tunnel which is subject to the provisions of the Quarries and Tunnels Act 1982.
(b) Processing and manufacture of explosives
? Areas which may be affected by oxygen enrichment
(d) Areas where risks may arise due to the presence of combustible dusts (see Note 3); or
(e) Potential catastrophic failures such as the bursting of pressure vessels, pipelines or tanks.
NOTE-
(1) Normal atmospheric conditions include variations above and below reference levels of 101.3 kPa abs and 20 °C provided the variations have.a negligible effect on the explosion properties of the flammable materials.
(2)The design, construction and installation of plant and equipment have a significant bearing on classification. However, this Standard does not specify any requirements for such design, construction or installation.
(3) The classification of hazardous areas where combustible dusts are present (Class II areas) is covered in NZS 6101:Part 2.