What is ATEX directives / FM Approval / CSA approved / CE certified?

What is ATEX directives / FM Approval / CSA approved / CE certified ? What is the importance of individual certification? Are all these certification required for each instruments? Which certification do we prefer?

Answer -

ATEX/FM/CSA certifications generally refer to certification for suitability of instruments for use in hazardous area when installed in accordance with recommended guidelines. Any certification, which is locally acceptable as per statutory requirements, may be used. We typically accept American/European/Indian certifications/approvals in India.