Why Two Apparently Identical Plants Can Have Different Hazardous Area Classifications
Two production plants. The same raw material. The same process installation. The same production capacity.
Yet the hazardous area classification in accordance with the EN IEC 60079 series may be completely different.
At first glance, this seems contradictory. In reality, it reflects exactly how modern explosion safety is intended to work.
A hazardous area is not determined by the type of plant or the industry sector. Nor can an existing hazardous area classification simply be copied from one installation to another. Every hazardous area classification is the result of an independent engineering assessment of the actual operating conditions.
Far more factors influence the outcome than many people realise. The properties of the substance, the grade and source of release, process pressure, process temperature, ventilation effectiveness, operating procedures, the frequency and duration of releases, maintenance strategy and even relatively small design differences can significantly affect the extent—or even the existence—of a hazardous area.
Consider two plants that appear virtually identical. In one facility, valves and seals are replaced proactively, leaks are repaired immediately and the effectiveness of the ventilation system is regularly verified. In the other, maintenance is largely reactive, ventilation performance has deteriorated over time and process conditions have gradually changed. On paper, both facilities look the same. From an explosion safety perspective, however, they are fundamentally different.
This is precisely why EN IEC 60079-10-1 for gases and vapours and EN IEC 60079-10-2 for combustible dusts 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. Engineering judgement, practical experience and technical competence are therefore just as important as applying the standard itself.
For plant owners and duty holders, this has an important consequence. A hazardous area classification is not a document that is completed during a project and then filed away indefinitely. Under the ATEX Workplace Directive (1999/92/EC) within the European Union, and under the Dangerous Substances and Explosive Atmospheres Regulations (DSEAR) in the United Kingdom, explosion risks must be reviewed whenever substances, processes, equipment, ventilation systems or operating conditions change. A hazardous area classification that is technically correct today may no longer be valid tomorrow.
Perhaps that is the most important lesson. Explosion safety is not about copying a hazardous area classification—it is about understanding why that classification was established in the first place. The real value of a hazardous area classification is not the drawing itself, but the quality of the engineering assessment on which it is based. That is exactly why two apparently identical plants can legitimately have different hazardous area classifications.
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 1127-1 – Explosion Prevention and Protection
- BS EN IEC 60079 Series (United Kingdom)