Modifying and recertifying equipment for Explosive Atmospheres IEC 60079
In our company we develop products for zone 1 and 2. The functional aspect does not change much compared to the conventional design, however, safety and robustness play a big role here and so does the selection of components.

There are probably companies out there, which could take up the challenge to make your device meet zone 1 and/or zone 2 requirements. They would have to be specialized in such field, because it involves meeting several complex requirements, and usually a standards expert is among the main characters in the designing loop. 

Due to the stringent component selection, it is often not feasible to reuse an old design. What is done some times, is to buy small modules as black-boxes which have already been certified for zone 1 and/or zone 2 (saves time and money). If that is not possible, as it is the case with passive elements, it is up to the designer and standard expert to determine what are the implications of using such components in case of failure. Sometimes it can get a bit more complicated, if you have other companies producing a part for your design, for example a transformer. If it is not a client specific design, they also would have to change their design to meet your needs.

Below are a few examples of implications or aspects which should be considered while designing such electronics:


Galvanic Isolated Power Supply: failing to regulate and monitor the output voltage / current, can lead to a unpredictable behavior, which in turn can expose energized pins to a explosive atmoshpere.
Limited capacitance: Maximum stored energy in the device must be limited
Fuse selection is much stringent due to lower and upper limits
Temperature monitoring of the critical (if not all) components is sometimes a must


As described here, there are different types of certifications and approaches to certify your product. I believe, the best approach would be:


Have your requirements predefined (where to use the device, at what conditions and so on)
Have your requirements checked by a standards expert. He will then say what standards and specific requirements will have to be met
Come up with a design and all counter measures.
Even before you start the design, involve a certification body (who is going to certify your product) in the loop, to check whether it is even feasible to have your product certified later. Based on their experience, they might as well give your hints.
Then, and only then, start with your design.


I hope it helps