Area classification-an alternative approach

The present technique for defining hazardous areas in the UK is based on the UK Code of practice BS 5345 Parts 1 and 2, and the IEC Standard 79-10. A European Standard EN 50 145 will be published shortly. With minor exceptions, these documents treat the subject in the same way, and lead to similar results. The key aspects to note at the outset are: (a) that there are three zones (zone 0, zone 1 and zone 2); (b) that the zone number is a function of the likelihood of occurrence and duration of hazardous release; (c) that the extent of the zone is the distance from the source of release to the point (locus) at which the hazard disperses to a concentration less than the Lower Explosive Limit (LEL); and (d) that the area classification exercise contains a requirement to carry out some element of hazard reduction where practicable