I should have been more clear.
Originally Posted by LeoJackson
It will either be non-incindive or intrinsically safe - not both.
Your answer will be in the Control Drawing or on the area classification drawing. Since you are doing the redesign, you are the engineer of record. You will either need to find, or draft those two documents.
A drawing or other document provided by the manufacturer of the intrinsically safe or associated apparatus, or of the nonincendive field wiring apparatus or associated nonincendive field wiring apparatus, that details the allowed interconnections between the intrinsically safe and associated apparatus or between the nonincendive field wiring apparatus or associated nonincendive field wiring apparatus.
(A) Documentation. All areas designated as hazardous (classified) locations shall be properly documented. This documentation shall be available to those authorized to design, install, inspect, maintain, or operate electrical equipment at the location.
This is generally the area classification drawing.
If I were doing the job, those would be the first two documents I would find.