When Is a Hazardous Area Classification No Longer Technically Defensible?
A hazardous area classification is often regarded as the final deliverable of a project. The facility has been commissioned, hazardous areas have been classified, and the drawings are filed away. From that point onwards, the focus shifts to production, maintenance and operational availability.
Yet this is precisely where an important question arises.
How long does a hazardous area classification remain technically defensible?
A hazardous area classification is not an inherent characteristic of a plant or process. It is the outcome of an engineering assessment based on the actual operating conditions at a specific point in time. That assessment considers the properties of the substances handled, the sources and grades of release, process conditions, ventilation effectiveness, operating practices and the way the installation is managed. If any of these parameters change, the technical basis of the original hazardous area classification may also change.
In practice, industrial installations are continually evolving. Production processes are optimised, formulations are modified, plant capacities are increased, ventilation systems are upgraded, valves are replaced, piping is rerouted and automation systems are expanded. Although these changes are often introduced to improve reliability, efficiency or productivity, they may also influence the likelihood, duration or extent of an explosive atmosphere.
This is exactly why EN IEC 60079-10-1 for explosive gas atmospheres and EN IEC 60079-10-2 for combustible dust atmospheres do not prescribe standard hazardous area classifications. Instead, they provide a structured engineering methodology that enables competent specialists to evaluate the actual operating conditions and justify their conclusions. Hazardous area classification is therefore never a standard solution—it is always the result of a technically substantiated engineering assessment.
Consequently, an existing hazardous area classification does not remain valid simply because it has not been revised. A drawing that was technically correct ten years ago may still accurately represent today's installation—but it may equally no longer reflect reality. Not because the standard has changed, but because the installation itself has evolved.
For plant owners and duty holders, this carries an important responsibility. Within the European Union, the ATEX Workplace Directive (1999/92/EC) requires explosion risks to be reviewed whenever changes to substances, processes, equipment or operating conditions may affect workplace safety. In the United Kingdom, equivalent responsibilities are established under the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR). The explosion protection documentation and hazardous area classification should therefore remain aligned with the actual condition of the installation throughout its operational life.
A hazardous area classification is therefore much more than a drawing. It forms the technical foundation for selecting suitable equipment, carrying out inspections in accordance with EN IEC 60079-17, planning maintenance activities and managing modifications through an effective Management of Change (MoC) process. Only by regularly reviewing these factors can the engineering justification for the hazardous area classification remain technically robust.
Perhaps this is the most important question every asset owner should ask on a regular basis.
Has our installation changed... or has only our hazardous area classification remained unchanged?
The answer determines whether a hazardous area classification is still technically defensible today. Explosion safety is not about preserving historic drawings; it is about continually demonstrating that the hazardous area classification reflects the actual installation. That is where engineering, asset integrity, Management of Change and professional explosion safety come together.
References
- ATEX Directive 2014/34/EU
- ATEX Workplace Directive 1999/92/EC
- UK Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR)
- EN IEC 60079-10-1:2021 – Explosive Atmospheres – Classification of Areas – Explosive Gas Atmospheres
- EN IEC 60079-10-2:2026 – Explosive Atmospheres – Classification of Areas – Combustible Dust Atmospheres
- EN IEC 60079-14:2024 – Design, Selection and Installation of Electrical Equipment
- EN IEC 60079-17:2023 – Inspection and Maintenance of Electrical Installations
- EN 1127-1 – Explosion Prevention and Protection
- BS EN IEC 60079 Series (United Kingdom)