In the UK there's BS EN 60079-19 which covers repairs of hazardous area motors. I believe it was written with the assistance of the electrical manufacturers industry bodies, BEAMA and the AEMT.
Correct Scotty, dates from a document drafted in1984, I was involved in a small way. It went on to be released as EN 60079-19.
I do not think that approval is a legal requirement, but AEMT do offer an approval service, which approves the management, I do not think it is a test house for the repaired motor or device.
Krysis, which country are you in, since this will probably affect the requirements.
This location is in one of the Middle Eastern countries. I would like to know whether such the motor workshop needs any certification to do the servicing of hazardous area motors.
In common with many of the British Standards it's not mandatory, but it is also the standard that a judge will refer to if something goes wrong. At that point you will be trying to explain why you know better than the standards committee, and the fact that you're explaining to a judge in the first place means that you almost certainly didn't know better than the standards committee because it went wrong... at least if you follow the standards then you have some plausible defence if the worst happens.
The problem is as Scotty says, in UK, Europe and countries which follow our systems, known as "the IEC / ISO" world, then when it all goes wrong you, have to demonstrate that you have employed a Competent Person to assess the risks and make appropriate decisions.
The decision in the UK in your example, couuld be that as there is no specific requirement for repairers who are approved is to find one who is competent, either by being a member of an approval scheme, or who is experienced, for example being a repairer who has performed work for someone like Shell Petroleum.
There is a lot of assistance on the UK's Health and Safety Executive's website, eg:
