Intrinsic Safety (IS) is a protection technique for the safe operation of electrical equipment in hazardous areas. IS equipment is designed to be incapable of releasing sufficient electrical or thermal energy to cause the ignition of a hazardous atmospheric mixture.
A gas detector in an IS loop will be designed so that even in a fault condition, it cannot ignite a flammable atmosphere. This includes limiting the energy stored in the device and making sure that any arcs, sparks, or hot surfaces that could occur inside the device cannot ignite a flammable atmosphere.
However, not all gas detectors are part of IS loops because not all gas detectors are located in areas where an explosive atmosphere might be present. IS-rated equipment tends to be more expensive due to the additional design considerations and certifications required, so if a detector isn’t in an explosive atmosphere, a non-IS detector might be chosen to save cost.
In many instances, gas detectors are part of IS loops. The decision whether to use IS depends on the classification of the area where the detector is installed, the nature of the gases detected, and the potential for those gases to form an explosive atmosphere. Regulations, standards, and best practices dictate when and where IS should be used.
In all cases, whether for SIL rating, wiring configurations, or IS considerations, the specific requirements of the operating environment, relevant safety standards, and local regulations should always be followed. Always consult with a safety engineer or other qualified professional when making these types of decisions.