arpadveress 
Terminal boxes and switches in intrinsically safe circuits can be assumed to have a temperature rise of less than 40 K and can thus have a temperature classification of
- T6 at ambient temperature not exceeding 40 °C,
- T5 at an ambient temperature not exceeding 55 °C or
- T4 at an ambient temperature not exceeding 80 °C.
So ambient conditions have their influence on safe operation even if intrinsically safe.
Keep up good work!
Arpad
