arpadveress 
Part of standard atmospheric conditions is the temperature, which shall be between –20 °C to +60 °C.
Although the standard atmospheric conditions above give a temperature range for the atmosphere of -20 °C to +60 °C, the normal ambient temperature range for the Ex Equipment is –20 °C to +40 °C, unless otherwise specified and marked. It is considered that –20 °C to +40 °C is appropriate for many items of Ex Equipment and that to manufacture all Ex Equipment to be suitable for a standard atmosphere upper ambient temperature of +60 °C would place unnecessary design constraints.
Defined in IEC 60079-0 in order to avoid any misunderstanding. If there is any change, it shall be documented.
Keep up good work.
Arpad
exprofessional.com
