The Ex d e protection method is in general for use in Zone 1.
You are not telling what kind of Ex Box you have. Is it an Ex d or Ex e box?
If it's an Ex d box you don't have to use a Ex protected circuitbreaker at all, but the combined system has to be certified as a complete unit.
If it's an Ex e box you have to check the documentation for the box to see what's alowed to put in it.
You should also check the documentation for the circuitbreaker regarding the specified conditions for the installation of it.

Hello again.

Its an Ex e II T5 box

The Ex e II T5 box is certified as manufactured, but it might be alowed to add equipment to it. Check what is stated in the documentation for the box to find out what you can add, if anything.
It's not the case as many believe that you can put anything into a box just because it is Ex-certified. The T5 approval for the box quickly gets invalid when you add extra equipment and power, and thus extra heat. And then you don't have a Ex-approved box anymore...
Therefore you should always check the documentation for the equipment, even if it's ""just a box"".