Which are the constraints that should be taken into consideration when using an oil in an ATEX zone?

Some industries, by their nature, are subject to a particularly high risk of explosion.
For combustion to occur, the following three elements are required:
– fuel in a finely dispersed form (vapour, gas, powder, fog, etc.). Oil can only play this role when it is used at temperatures that are higher than its flashpoint. This is only the case in heat transfer circuits. These should have their own specific risk analysis carried out on them.
– an oxidant, usually the oxygen in the air
– an ignition source to provide the minimum ignition energy
In industry, the oxidant is usually the oxygen in the air and the fuel is usually the one used in the manufacturing process: gas, steam, dust, etc. The purpose of the standards pertaining to equipment for use in ATEX zones is to prevent an ignition source from being brought into them by using equipment that has been specially protected in these zones. 
Although there are no oils that have been specifically formulated for use in ATEX zones, oils play a particularly important role in insulating certain pieces of equipment, such as electrical transformers or electric motors submersed in oil. It should be ascertained in such cases that the lubricant's breakdown voltage is suitable. For oil circulation systems used in ATEX zones, electrostatic discharges should be avoided if the oil used has low conductivity.