HomeInstrumentationIntrinsic Safety (Exi) | A complete guide

Intrinsic Safety (Exi) | A complete guide

In this article I will explain intrinsic safety from my own experience and what are the considerations you have to take.


Intrinsic Safety is one of the protection methods that is used to prevent explosion hazards due to electrical ignition sources. for a better understanding, I want to share my experience.

As per the client’s spec, all instruments should be Intrinsically safe. But the experienced Instrument person the client himself didn’t know about the whole meaning of Intrinsic Safety.

They just want Exia Transmitters but simply taking Exia certified transmitter will not justify an Intrinsic safe system. When I didn’t have that much experience I also thought like that.

But when I saw many detailed references I found out that it is not as simple as it looks. Because of that, I Wrote this article for you and for those who

but they didn’t know if you are talking about intrinsic safety you have to consider the whole loop from cable to barriers to all connected instruments in this loop.

What is an Intrinsic safe system?

NEC Define IS as Below

Intrinsically safe equipment and wiring shall not be capable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific flammable or combustible atmospheric mixture in its most easily ignitable concentration.

Simply Intrinsically safe system limits the energy that will create spark or heat that ignites flammable gases in the field.

I am not going too technical(Energy level, Certification of Exi Devices, Fieldbus Intrinsically Safe Concept, etc.) side you can refer to my attached reference that will help you to understand more about this.

How to define an Intrinsic safe system?

  1. You have to take all loop components in the count and then find out what the components are. Thermocouples and RTD are safe because both themselves didn’t generate any spark or thermal level. But because it is connected to the transmitter but could happen that the transmitter allows a dangerous amount of energy to reach at TC tip.
  2. Then you have to check and compare the electrical parameters of cable, instrument, and safety barriers and after getting this data you have to check that the below conditions will fully fill.
Barrier ParametersInstrument Parameters
UoMax output voltage< UiMax input voltage
IoMax output current< IiMax input current
PoMax output power< PiMax input power
CoMax load capacitance> Ci + Cc (Ci instrument capacitance
Cc is the cable capacitance)
Lo inductance> Li + Lc (Li instrument inductance
Lc is the cable inductance)
Conditions of Intrinsic Safe System

When you see the above condition cable selection and cable length are very important because the electrical data of the instrument and Barrier is fixed.

You can find the electrical parameters of the barrier from the vendor data sheet I shared one example PDF file you can find data on page No. 3

When you talk about Barriers there are only 3-4 Major vendors in the market mentioned below.


You can find the electrical parameters of the transmitter from the ATEX certificate I attached one ATEX certificate for your reference.

And in the last and the most important, electrical data of cable, you can find from Cable GTP provided by the vendor. You can check out from attached Sample Cable GTP from the Vendor.


Recently, I also found this interesting Handbook on Intrinsic Safety, and this book includes examples of how to verify intrinsic safety.


I hope these resources and Knowledge will become helpful to you in the future. And I continue to make this type of resource and knowledge-sharing posts on my website.

If you have any suggestions then feel free to ask in the comments and through email ID, if you want to write an article on the website, please contact us by this email id: contact@worldofinstrumentation.com

If you like this post you can also like my previous article on Hazardous area classification.

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KISHAN MENDAPARAhttps://worldofinstrumentation.com
Instrumentation and Control Engineer

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