CompEx Units Explained — Ex01 Ex02 Ex03 Ex04 Ex05 Ex06
CompEx is divided into units, each covering a specific scope of work. Understanding which units you need for your role — and what each covers — is the starting point for your CompEx preparation.
CompEx Units Overview
| Unit | Scope | Gas Groups | Who Needs It |
|---|---|---|---|
| Ex01 | Installation of Ex equipment | IIA and IIB | Electricians installing Ex equipment on most process sites |
| Ex02 | Installation of Ex equipment | IIC (hydrogen, acetylene) | Electricians on hydrogen facilities, LNG, coke ovens |
| Ex03 | Inspection of Ex equipment | IIA and IIB | Inspection engineers, maintenance electricians |
| Ex04 | Inspection of Ex equipment | IIC | Inspection engineers on IIC sites |
| Ex05 | Instrumentation (intrinsic safety) | All groups | Instrument technicians working with IS systems |
| Ex06 | Cathodic protection systems | All groups | Cathodic protection engineers |
Ex01 — Installation IIA/IIB
Ex01 covers the installation of electrical equipment in gas hazardous areas for gas groups IIA and IIB. This includes equipment selection, cable gland specification, earthing, and documentation. Based on IEC 60079-14. Required for any electrician installing Ex equipment on process plant, offshore, or chemical sites where IIA or IIB gases are present.
Ex02 — Installation IIC
Ex02 extends Ex01 to cover the additional requirements of IIC gas group areas — hydrogen, acetylene, and carbon disulphide. The core content is the same as Ex01 but with additional focus on the critical rule that every component in an IIC area must be IIC certified, and the tighter flamepath gap requirements for IIC Ex d equipment.
Ex03 — Inspection IIA/IIB
Ex03 covers the inspection and maintenance of Ex equipment for gas groups IIA and IIB. Based on IEC 60079-17. The most commonly held CompEx unit alongside Ex01. Covers inspection grades (Visual, Close, Detailed), deficiency classification (Category X, A, B, C), and inspection documentation.
Ex04 — Inspection IIC
Ex04 extends Ex03 to cover IIC gas group areas. Additional knowledge of IIC-specific requirements — tighter flamepath gaps, IIC component requirements, and the additional inspection implications of hydrogen environments.
Ex05 — Instrumentation and Intrinsic Safety
Ex05 covers intrinsically safe systems, Zener barriers, galvanic isolators, entity parameters, IS earthing and segregation, and the inspection of IS systems. Required for instrument technicians designing, installing, or maintaining IS loops in hazardous areas.
Most process plant and offshore electricians require Ex01 and Ex03 as a minimum. If your site has IIC areas (hydrogen, LNG, acetylene), add Ex02 and Ex04. If you work with IS instrumentation, add Ex05. Speak to your employer or the CompEx assessment centre for advice on which units apply to your specific role and site.
Interactive inspection simulations, equipment selection decisions, and 1,185+ practice questions referenced to IEC 60079. Try free — no card required.
Try the Platform Free →More Articles