Hazardous Area Classification and Ex Inspection in Tunisia: A Practical Guide for Plant Operators
In short: a hazardous area classification (HAC) study maps where an explosive atmosphere can form on a site and how often. Ex inspection then checks, over the whole life of the installation, that every piece of equipment installed in those zones is still suited to them and in good condition. Both are carried out according to the IEC 60079 series of standards, which international operators in Tunisia and North Africa apply alongside the European ATEX directives.
Oil and gas facilities, gas storage and filling stations, chemical plants, grain silos, flour mills and many food factories all handle flammable gases, vapours or combustible dusts. On these sites, a spark from an unsuitable motor, junction box or instrument can be enough to cause an explosion. This guide explains how a HAC study and an Ex inspection programme work, and what an operator should expect from them.
What is hazardous area classification?
Hazardous area classification is the risk assessment that divides a facility into zones according to the probability and duration of an explosive atmosphere being present. It is the basis for selecting, installing and maintaining every piece of electrical and mechanical equipment in those areas. For gases and vapours it follows IEC 60079-10-1, and for combustible dusts IEC 60079-10-2.
| Presence of an explosive atmosphere | Gas and vapour | Combustible dust |
|---|---|---|
| Continuous, for long periods or frequently | Zone 0 | Zone 20 |
| Likely to occur occasionally in normal operation | Zone 1 | Zone 21 |
| Not likely in normal operation, and only for a short period if it does | Zone 2 | Zone 22 |
How a HAC study is carried out
- Identify the flammable substances handled on site and their properties: flash point, ignition temperature, explosion limits, gas group or dust characteristics.
- Locate the sources of release: flanges, pump seals, vents, sampling points, loading arms, dust transfer points.
- Assess the grade of each release (continuous, primary or secondary) and the effectiveness of ventilation.
- Classify the zones and define their extent, then draw them on the plant layout.
- Specify the equipment allowed in each zone: equipment protection level, gas group and temperature class.
- Report the results in a HAC report with its drawings, which becomes the reference for design, purchasing and maintenance.
The study has to be reviewed whenever the process, the substances or the layout change. A classification that no longer matches the plant is one of the most frequent gaps found during audits.
What an Ex inspection checks
Once equipment is installed, IEC 60079-17 requires it to be inspected throughout its life. The standard defines three grades of inspection:
- Visual inspection: carried out without tools or opening the equipment, it detects visible defects such as missing bolts, damaged cable glands, corrosion or missing labels.
- Close inspection: adds checks that need access equipment and tools, such as the tightness of fixings and connections, without opening the enclosure.
- Detailed inspection: the enclosure is opened, with the circuit isolated, to verify the internal condition and the protection concept.
An initial inspection is required before first use, and after any modification. Periodic inspections follow, at an interval set by the operator according to the environment, vibration, corrosion and the history of findings. Some operators complement them with sample inspections to confirm that the chosen interval is still appropriate.
Findings that come up most often
- Equipment whose marking does not match the zone, gas group or temperature class of its location.
- Cable glands, plugs or seals replaced with non-certified parts.
- Enclosures modified on site (extra holes, removed gaskets) that lose their protection.
- No up-to-date register of the equipment installed in hazardous areas.
Why the competence of the people involved matters
IEC 60079-14 and IEC 60079-17 require the people who design, install, inspect and maintain Ex installations to be competent in the protection concepts they work on, not only qualified as electricians. In practice, operators look for recognised certifications such as the IECEx personnel competence scheme or, in the French-speaking world, the Ism-ATEX scheme run by INERIS, which defines levels from site personnel to trainers.
At IMSR, our team includes an INERIS-certified Ism-ATEX Level 3 trainer, the level authorised to train and assess personnel. Our ATEX training courses are delivered on that basis.
How IMSR supports operators
From our base in Sfax, IMSR Engineering supports industrial operators across Tunisia and North Africa at every stage:
- Hazardous area classification studies according to IEC 60079-10, with zone drawings and a full HAC report.
- Selection of ATEX equipment, supervision of works and installation according to IEC 60079-14.
- Audit and Ex inspection of existing installations, with a register of ATEX equipment and a corrective action plan.
- Instrumentation and automation for hazardous areas.
- Professional ATEX training for operators, technicians and supervisors.
Frequently asked questions
Who is responsible for the classification of hazardous areas?
The operator of the site. The study can be carried out by a specialised engineering company, but the operator remains responsible for keeping it up to date and for making sure equipment matches it.
How often should Ex equipment be inspected?
IEC 60079-17 does not set a single interval. The operator defines it from a documented assessment of the environment and of past findings. A common starting point is a periodic inspection every three years, adjusted afterwards.
Do ATEX rules apply outside the European Union?
The ATEX directives are European law, but the IEC 60079 standards on which they rely are international. Many operators in Tunisia, Libya and Algeria, especially in oil and gas, require their contractors to work to IEC 60079 and to ATEX or IECEx certified equipment.
What is the difference between ATEX and IECEx?
ATEX is the European regulatory framework for equipment and workplaces. IECEx is an international certification system for equipment, service facilities and personnel competence, based on the same IEC 60079 standards.
Need a HAC study, an Ex inspection or ATEX training on your site? Contact our team or write to contact@imsr-eng.com.
