How Is ATEX Risk Analysis Carried Out?

For a piece of equipment to be considered safe under ATEX, it must be demonstrated that all possible ignition sources have been systematically assessed and brought under control. This study is called an "ignition hazard assessment" and is one of the most critical components of the ATEX technical file. In this article we explain how this analysis is carried out.

How ATEX Risk Analysis Differs From General CE Risk Analysis

A standard CE/machinery risk analysis covers mechanical, electrical, thermal, ergonomic and many other hazard categories (see How Is Risk Analysis Carried Out?). The ATEX ignition source analysis, as a complement to this, focuses specifically on whether the equipment contains sources that could ignite an explosive atmosphere. These two analyses are generally carried out together, but as separate documents.

Ignition Sources That Must Be Assessed

• Hot surfaces: Ensuring that heatable surfaces such as the motor housing, rubbing parts and electronic components do not exceed the limits of their temperature class (T1-T6).
• Flames and hot gases: The risk of direct flame or hot gas discharge in equipment involving a combustion process.
• Mechanical sparks: Sparks that can be created by metal particles as a result of friction, impact or wear.
• Electrical sparks and arcing: Electrical arcs that can occur during switching, a loose connection, or a fault condition.
• Static electricity: Static charge that accumulates and discharges, particularly during plastic, dust or liquid transfer processes.
• Stray electrical currents: Unwanted currents originating from cathodic protection systems or welding operations.
• Lightning: High-energy discharges that can occur from direct or indirect lightning effects.
• Radio frequency (RF) electromagnetic waves: High-power RF transmitters inducing current in certain sensitive circuits.
• Ultrasonic energy and adiabatic compression: Sources specific to certain industrial processes, less common but not to be overlooked.
• Chemical reactions: Exothermic reactions that could occur inside or on the surface of the equipment.

The analysis determines which of these sources are relevant depending on the equipment's protection type; for example, in an intrinsically safe (Ex ia) circuit the priority is limiting electrical energy, while in a flameproof (Ex d) enclosure the priority is preventing a possible internal explosion from spreading outward.

How Is the Analysis Carried Out?

1. All components of the equipment and its operating principle are technically examined.
2. Which ignition sources could occur under normal operating conditions is listed.
3. Foreseeable fault scenarios (for example, a bearing overheating, a connection loosening) are assessed.
4. For each source, it is demonstrated how the chosen protection type controls that source.
5. Where necessary, the analysis is verified through laboratory tests (temperature measurement, pressure resistance, energy limitation testing, etc.).
6. The results are documented in an "ignition source analysis report" that becomes part of the technical file.

Depth of Analysis by Category

The scope and depth of the analysis increases in proportion to the equipment category. For Category 3 equipment, normal operating conditions are generally assessed; for Category 2, common faults are added to this; and for Category 1, rare multiple-fault scenarios are also included in the scope of the analysis. This differentiation is consistent with the zone-equipment matching that is a direct result of the category system; see What Are Zones 0, 1 and 2?.

Frequently Asked Questions

Conclusion

ATEX ignition source analysis is the fundamental engineering study that shows whether a piece of equipment is genuinely safe in an explosive atmosphere. Carrying out this analysis systematically and completely is decisive for both legal compliance and real safety in the field.