---
title: Marking
description: "**Associated apparatus not suitable for installation in a hazardous area** will be certified and marked with the Ex symbol and the type of protection, all within the same square brackets: **e.g. [Ex ia] IIC** For **associated apparatus suitable for installation…"
url: "https://www.eicstech.com/kb/intrinsic-safety-ex-i/basics-on-intrinsic-safety/"
updated: "2022-06-01"
category: Explosion Proof Basics / Intrinsic Safety (Ex i)
---

# Marking

**Associated apparatus not suitable for installation in a hazardous area** will be certified and marked with the Ex symbol and the type of protection, all within the same square brackets:

**e.g. [Ex ia] IIC**

For **associated apparatus suitable for installation in a hazardous area,** and where the energy limitation is provided inside the equipment in the hazardous area, the symbols of the type of protection are enclosed within square brackets:

**e.g. Ex d [ib] IIC T5 or Ex px [ia] IIB T4**

This marking would means; **the enclosure is flameproof and contains associated ‘intrinsically safe’ equipment.**

**Certified intrinsically safe field equipment**, for mounting in the hazardous area, will be **marked** with the type of protection in the normal way:

**e.g. Ex ia IIC T6 Ex ib IIC T5 Ex ic IIB T4**

**Simple Apparatus** is not required to be marked.