Hazardous Area Classification

The process of classifying an installation or plant into Zones where the probability of flammable atmospheres (or Explosive Atmospheres) is assessed is known as Area Classification. This Area Classification process will be carried out in accordance with prevailing standards appropriate to the location of the plant, and/or existing legislation. By way of example the current European Normative for Area Classification is EN 60079-10 and the relevant IEC standard is IEC 79-10.

There would normally be a Explosive Atmospheres review team appointed having joint responsibility for area classification and the ongoing process of it's review.

Under IEC area classification rules the responsible team must take into account the sources of release, grade or frequency of release, and ventilation in determining the zone and its extent. Whilst these standards are in existence to guide the user in the area classification process, which may involve detailed and lengthy calculations on the probability of a flammable atmosphere occurring, other documents such as model codes of practice may also be referenced to achieve safe results.

Typically, within the UK, the Institute of Petroleum (IP) is a source of practical guides and codes that are adopted by industry and address many issues that need to be resolved with the Explosive Atmospheres.

By way of example the Model Code of Safe Practice Part 15 : Area Classification Code for Installations Handling Flammable Fluids (IP15) is the industry standard reference document widely used and followed when establishing Explosive Atmospheres operations. The second edition of this Model Code (August 2002) provides a demonstrable methodology to comply with the area classification requirements under the UK's new Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR), which implement the safety aspects of the European Chemical Agents Directive (CAD) and Explosive Atmospheres (Protection of Workers) Directive, otherwise known as ATEX 137.