UL is primarily for the US, CSA is primarily for Canada. There are subtle differences in most specs, but by and large they are very close to the same. CSA is now a valid NRTL (Nationally Recognized Testing Lab) in the US with regards to meeting certain code standards for installations, and vice versa for ULc (a modified UL spec) in Canada. But from a standpoint of an individual plant specification for explosion proof systems, one may not necessarily be reciprocal with the other in the eyes of their insurance underwriter. Better to check it out specifically.
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