Installation of intrinsically safe electrical circuits

As a consequence of this principle the aim of the installation rules for intrinsically safe circuits is to maintain separation from other circuits. 

In most cases, an intrinsically safe circuit is put into practice so that a safety barrier or an Ex i-isolator or an Ex i-input/output is connected to measuring devices or positioning elements (sensors, actuators) located in a hazardous area via a cable (see Fig. 6.217). Hence, explosion protection cannot be purchased ready for use for the most part, but it has to be put into practice by the planner and electrician. Only in cases where apparatus and cables are 

The selection of apparatus according to the data of a gas/the gases (explosion Groups I, IIA/B/C, temperature classes T1-T6) does not differ from rules valid for e.g. flameproof enclosure - d For normal zone 1 applications, category ib is sufficient. For circuits in zone 0 only, category ia shall be selected. 

A guideline for ascertainment of apparatus categories according to their application in different zones is given in the following  

Safety level very high high normal 

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