Specifies requirements relating to design, construction, testing and marking of electrical equipment which can be shown by test or assessment to be suitable for use in explosive gas atmospheres. It is may be used by certification bodies in the testing and/or assessment of equipment for certification.

This Interim Standard specifies requirements relating to the design, construction, testing and marking of electrical apparatus or parts thereof which can be shown by test or assessment to be suitable for use in explosive gas atmospheres.It is applicable to Group I and Group II as defined in AS/NZS 60079.0.It is applicable to apparatus intended for Zone 0, Zone 1, or Zone 2 as defined in AS/NZS 60079.10. The apparatus shall be designed tested and marked according to the Zone for which it is intended.This Interim Standard supplements the general requirements in AS/NZS 60079.0 and the requirements of the standardized types of protection, in accordance with the AS/NZS 60079 series.This Interim Standard shall not be used for apparatus or any parts of apparatus that could be designed and tested to one or more existing explosion-protection techniques as described in AS/NZS 60079 series or IEC equivalent, or to combinations of techniques as described in AS/NZS 60079.26. This Interim Standard shall not be considered as a last resort in the event that apparatus fails compliance to the 60079 series. This may mean that modification of the design will be necessary to meet the requirements of the established techniques. This Interim Standard may also be used to design and test apparatus that is required to be used in a Zone of higher hazard than the underlying protection techniques allow. This shall require additional control measures to be applied, or additional design and test requirements to be applied.Ex ’s’ shall only be considered where design options are limited for technical, operational or functional reasons.Parts of apparatus that can be designed and tested to standardized techniques should be so designed. Only those parts that achieve safety through alternative controls should be considered for Ex ’s’.An example where technical, operational or functional limitations preclude recognized techniques being used is in gas detectors for Zone 0, using heated filaments: The major part of the apparatus can comply with Ex ’ia’, but in order to function, the filaments, which are ignition sources, have to be exposed directly to the gas. The gas has to get to the filaments by diffusion or aspiration. In either case, the protection is to contain flame or explosion. This protection can only consist of one or more porous metal screens. These are permitted in Ex ’d’, but that protection technique is limited to Zone 1. A second layer of a different type of protection (as permitted in AS/NZS 60079.26 for Zone 0), is not physically possible, as it cannot permit free access of gas. Ex ’s’ is therefore the only solution for this part of the gas detector.The manufacturer shall demonstrate that the apparatus cannot be designed to one or a combination of existing techniques.A testing station may vary one or more of the requirements and tests specified herein provided that it is satisfied that the apparatus complies with alternative requirements or test procedures which are acceptable on the basis that they provide an equivalent or improved level of safety. Additional tests may be required by the testing station. The alternative requirements referred to above may be proposed by the apparatus manufacturer .Apparatus complying with this Interim Standard and operating within the operational parameters specified by the manufacturer ensures a level of protection commensurate with the Zone of hazard of the intended application.Where the apparatus is intended for Zone 0, the design requires a very high level of protection that includes consideration of rare faults related to the apparatus or two faults occurring independently of each other.A fault may result from a failure of the component parts of the electrical apparatus or from anticipated externally applied influences. Two independent malfunctions which may occur more frequently and which, separately, would not create an ignition hazard but which, in combination, could create a potential ignition hazard, should be regarded as occurring together to form a fault.In designing apparatus for operation in explosive gas atmospheres under conditions other than the atmospheric conditions given in AS/NZS 60079.0, this Interim Standard may be used as a guide. However, additional testing related specifically to the intended conditions of use is recommended. This is particularly important when the types of protection ‘Flameproof enclosure’ (AS/NZS 60079.1) and ‘Intrinsic safety’ (AS/NZS 60079.11) are applied. Such conditions might include hypobaric, hyperbaric and oxygen enriched atmospheres.There may be other non-electrical sources of ignition (for example ultrasonic, optical or ionizing radiation) that are not addressed by this Interim Standard; these should also be taken into consideration. (see, for example, EN 1127-1).The classification of hazardous areas in Zones is defined in AS/NZS 60079.10.

Originated as AS 1826-1976.Previous edition 1983.Revised and redesignated AS/NZS 1826(Int):2006. Originated as AS 1826-1976. Previous edition 1983. Revised and redesignated AS/NZS 1826(Int):2006.