Difference between IS and Non IS


VERY SIMPLY, IS (which stands for Intrinisically Safe) refers to methods for limiting the amount of current which might result in the ignition of combustible (hazardous) materials/atmospheres (areas) which wires pass through in order to try to prevent fires and explosions.

There are technical regulations and standards for some sites and applications (such as areas where natural gas is present--particularly if the natural gas is NOT odorized) where IS methods and so-called "barriers" (devices installed to limit current to try to prevent sparks and arcs that may ignite fires and/or explosions in unusual situations in hazardous areas) are legally required to be installed and used.

IS is typically used for control and protection circuits and wires/cables--again that pass through areas where hazardous atmospheres/materials (combustible).

In some parts of the world, IS-protected circuits are required to be indentified with specific colors of cable/core insulation to aid in maintenance/troubleshooting to protect against accidentally causing fires/explosions and negatively impacting control and protection of the equipment/process. (Light blue, or cyan, is a commonly-used insulation color for such purposes.)

Again, this is a VERY simplistic description. There are MANY related technical regulations and standards around the world related to this subject. IS equipment and practices have not always been in use, and there are sites where it is seemingly haphazardly used--usually when new equipment is added to the plant or process it is required to use IS methods and practices, or when cables are replaced for some other purpose (but not just to install IS equipment). So, in other words, older plants are not always required to replace older wires and cables and junction boxes and devices to come into compliance (this is often called "grandfathering").

Hope this helps!