Most engineers start with Ex 001 and Ex 002. The right unit depends on your job role. Field technicians need Ex 002. Design engineers need Ex 003. Safety engineers need Ex 004. Instrumentation specialists need Ex 007.
Picking the wrong IECEx unit wastes time and money. Picking the right one opens doors at ADNOC, Saudi Aramco, Qatar Energy, and major EPC contractors.
You already know IECEx certification is expected in oil and gas, petrochemicals, and any site with explosive atmospheres. What’s less clear is which unit—Ex 001 through Ex 010—actually fits your work.
This post breaks down every unit. It maps each one to a real job role and gives you a step-by-step way to choose. For the full certification path, read
the complete IECEx certification guide
before you pick a unit.
What Are IECEx Competency Units?
IECEx competency units are learning and assessment modules within the IECEx Certificate of Personnel Competence (CoPC) scheme. Each unit covers one area of hazardous area work—from equipment construction to optical radiation systems.
The scheme is modular. You earn certification in the units that match your actual work. You don’t sit for subjects that don’t apply to your role.
Each unit links to specific IEC 60079 standards. An accredited IECEx Certification Body (ExCB) assesses you. Your certificate goes into the IECEx On-Line Certification System (OCS). Employers and project owners can verify it there.
Unit-by-Unit Breakdown: What Each IECEx Unit Covers
The table below shows every IECEx competency unit, its name, and who it’s for.
| Unit Code | Unit Name | Who It’s For |
| Ex 00 | Awareness Level | Personnel near hazardous areas who don’t handle Ex equipment directly |
| Ex 001 | Equipment Construction and Verification | Equipment selectors, specifiers, and procurement engineers |
| Ex 002 | Installation, Inspection and Maintenance | Field technicians, electrical engineers, and maintenance staff |
| Ex 003 | Design Verification and Documentation Assessment | Design and project engineers on hazardous area projects |
| Ex 004 | Area Classification | Safety engineers, HSE professionals, and plant designers |
| Ex 005 | Flameproof Enclosures “d” | Specialists who maintain or specify flameproof equipment |
| Ex 006 | Increased Safety “e” | Motor and rotating equipment specialists |
| Ex 007 | Intrinsic Safety “i” | Instrumentation, control, and loop engineers |
| Ex 008 | Pressurization and Continuous Dilution | Specialists working with pressurized and purged systems |
| Ex 009 | Dust Ignition Protection | Personnel in flammable dust environments |
| Ex 010 | Optical Radiation Ignition Protection | Specialists using fiber optic or optical systems in hazardous areas |
Which IECEx Unit Fits Your Job Role?
The right unit depends on what you do—not what your job title says. Here’s how units map to real roles.
IECEx Ex 001: Equipment Construction and Verification
Ex 001 covers how manufacturers design and build Ex-certified equipment. You’ll learn about flameproof enclosures (Ex d), increased safety (Ex e), intrinsic safety (Ex i), pressurization (Ex p), and encapsulation (Ex m).
Best for: Engineers and procurement specialists who select or specify Ex equipment. If you review datasheets, compare protection types, or approve purchases for hazardous area projects, start here. Many candidates pair Ex 001 with Ex 002 for a stronger base.
IECEx Ex 002: Installation, Inspection and Maintenance
Ex 002 is the most commonly held unit in the region. It covers the full equipment lifecycle—installation per IEC 60079-14, inspection per IEC 60079-17, and maintenance per IEC 60079-19.
Best for: Field technicians and site engineers who install, inspect, or maintain Ex equipment. ADNOC contractors and Saudi Aramco project teams list Ex 002 as a key competency. If you do hands-on work in a classified zone, you need this unit.
The difference between Ex 001 and Ex 002 is simple. Ex 001 explains how equipment is built and why it’s safe. Ex 002 shows you how to install, check, and maintain it.
IECEx Ex 003: Design Verification and Documentation Assessment
Ex 003 covers reviewing hazardous area designs against recognized standards. This includes classification drawings, equipment selection records, and design documents—all checked before construction starts.
Best for: Design engineers and project engineers on EPC contracts. If you review or approve hazardous area design packages, Ex 003 gives you the tools to do it properly.
Before you start this unit, it helps to understand hazardous area zones and protection concepts in detail.
IECEx Ex 004: Area Classification
Ex 004 teaches you to assess release sources, determine release grade, account for ventilation, and assign the right zone—Zone 0, 1, 2, 20, 21, or 22—to each area of a facility.
Best for: Safety engineers, HSE managers, and plant designers who produce hazardous area classification drawings. Qatar Energy projects, for example, typically need zone classification drawings from Ex 004-certified personnel.
IECEx Ex 005–Ex 010: Protection Concept Specialist Units
These units go deep on one protection method each. Each one needs strong technical knowledge of its specific topic.
- Ex 005 – Flameproof Enclosures “d”: Flamepath design, joint tolerances, and Ex d maintenance per IEC 60079-1. Relevant for those who work on motors, switchgear, or control stations.
- Ex 006 – Increased Safety “e”: Terminal design, winding protection, and Ex e principles for motors and rotating equipment per IEC 60079-7.
- Ex 007 – Intrinsic Safety “i”: Intrinsically safe circuit design, barrier selection, and installation per IEC 60079-11. Essential for instrumentation and control engineers.
- Ex 008 – Pressurization and Continuous Dilution: Ex p systems, safety interlocks, and maintenance of pressurized enclosures.
- Ex 009 – Dust Ignition Protection: Dust-specific protection methods and equipment selection for Zone 20, 21, and 22.
- Ex 010 – Optical Radiation Ignition Protection: Fiber optic systems and optical radiation equipment in hazardous areas.
Signs You Need More Than One IECEx Unit
Not everyone needs just one unit. Check the list below. If two or more apply to you, a multi-unit plan makes sense.
- You select equipment (Ex 001) and install it on site (Ex 002)
- You design hazardous area systems (Ex 003) and classify the zones (Ex 004)
- Your site uses intrinsically safe loops (Ex 007) and pressurized control panels (Ex 008)
- You work in both dust environments (Ex 009) and gas/vapor zones (Ex 002)
- Your employer’s project specs list two or more units as required
- You manage a team and audit their work across multiple protection types
- You’re moving toward a senior role that spans design, installation, and inspection
