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11/05/2017 / Graham Lowe

SIL v. I.S. – What’s the Difference?

SIL v I.S.

Over the past couple of years, Hochiki Europe has extended its product offering to include ranges suitable for more specialist applications, for example SIL approved products and intrinsically safe products. However, not everyone is entirely familiar with what these ranges are designed for and when you would use them. We have therefore written this blog to quickly explain the differences between the two ranges.

First of all, it is important to note that SIL approved products are not the same as Intrinsically Safe Products. SIL approved products are for use in high risk industries, Intrinsically Safe products are for use in classified hazardous areas.

SIL Approved Devices:

S.I.L. is an acronym for ‘Safety Integrity Level’. This is a system used to quantify and qualify the requirements for safety instrumented systems.

All products, including fire detection products, must be independently assessed and approved by the International Electro-technical Commission (IEC); products will then be awarded a SIL approval level (SIL1, SIL2, SIL 3 and SIL4).

SIL graphic.png

For example, Hochiki’s SIL products have been awarded SIL2, which means that they are approved for use in a SIL2 low demand safety function. Please note however, a SIL approved panel must be installed with SIL approved devices in order for the whole system to meet the specified Safety Integrity Level.

SIL approved products are ideal for high risk areas that have specified SIL approved products.

Intrinsically Safe Devices:

For a product to be ‘Intrinsically Safe’ it must be incapable of igniting an explosive atmosphere by either spark or heat; Intrinsically Safe fire detection products are therefore designed to operate at a much lower voltage (even the quiescent current is much lower). This low power also means that there is no chance of receiving an electric shock due to excess thermal energy and arcing.

It is crucial to remember that, the whole circuit must be considered, not just the device in isolation and so an Intrinsically Safe mounting base must also be used.

If interfacing between hazardous and non-hazardous areas, you must use a module and an intrinsically safe barrier to reduce the current, but both the module and the barrier must be installed on the non-hazardous (safe) side.

IS graphic

Intrinsically Safe devices are ideal for hazardous-defined areas, oil refineries, petroleum production facilities, coal mining, gas processing, chemical engineering, air-borne powder facilities (flour, paper, synthetic fibres etc).

We hope this brief summary has been useful, for more information please visit:

One Comment

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  1. arul prasad J / Jul 1 2017 9:42 am

    thanks so much for giving brief info about IS and SIL. Helped me to understand the concept well. Regards , arul

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