arpadveress 
Cables used for fixed installations in hazardous areas shall be appropriate for the ambient conditions in service. Cables shall be:
a) sheathed with thermoplastic, thermosetting, or elastomeric material. They shall be circular and compact. Any bedding or sheath shall be extruded. Fillers, if any, shall be nonhygroscopic;
or
b) mineral insulated metal sheathed; or
c) special, e.g. flat cables with appropriate cable glands. They shall be compact and any bedding or sheath shall be extruded. Fillers, if any, shall be non-hygroscopic.
Where there is a likelihood that gas or vapour migration may occur through the interstices between individual cores of a cable, and the cable leads to a non-hazardous area or between different zones, then the construction and application of the cable shall be taken into account.
Appropriate control measures to mitigate this condition shall be considered – Test procedure:
A piece of cable with a length of 0,5 m should be type tested when installed into a sealed enclosure of 5 l (± 0,2 l), under constant temperature conditions. The cable is considered acceptable if the time interval required for an internal overpressure of at least 0,3 kPa (30 mm water gauge) to drop by 0,15 kPa (15 mm water gauge) is not less than 5 s.
The enclosure must be completely tight to avoid pressure loss through the enclosure gaps.
Where there is a likelihood that propagation of flames may occur through the interstices between individual cores of a cable, this shall also be considered.
Mineral insulated cables shall be sealed.
NOTE These requirements do not cover the selection of equipment for process sealing.
Many talk about compound cable glands and so on related to installation in possible hazardous environment.
What about the cable itself?
A/B/C options you may choose, conditions shall be confirmed by manufacturer, and still if there is likelihood… test shall be done if all conditions apply. Selection of right cable for Ex installation is not that simple.
Keep up good work.
Arpad
exprofessional.com
