Electronic Circuit Protection

1.When selecting an instrument for a chemical process plant, i am getting confused about the necessity of the surge protection of the transmitter. in some cases in the basic data sheet it is said yes and some cases it is said No, though instruments are going to be used for same environment, same process plant, and same power source. So is there some points so that i can be clear about this issue when should i select transmitter with or without surge protection?

2.If we use any barrier/isolator between hazardous and safe area instruments then should i consider the surge protection for instruments?