Hazards are part of our way of life and we instinctively take steps to protect ourselves and our property. The hazards present in the chemical and petrochemical industries, in the most part, are hidden from view so we have not developed the instincts for protection.
The hazards need to be studied defined and positive steps have to be taken to prevent disasters.
On a typical petrochemical site for example there are thousands of unseen hazards and ignition sources with potential explosion risks from gases, vapours and dusts which can cause catastrophic devastation when things go wrong. In order to prevent such incidents we need to define the hazard in order to control the explosive risk.
The starting point is EN 1127 part 1 Explosive atmospheres. Explosion prevention and protection. Basic concepts and methodology.
EN 1127 part 2 is for mining and outside the scope of this website.
The standards which dominate are the EN 60079 range which cover must aspects of the subject and are supplemented with the EN 80079 range, primarily for mechanical systems.
The EN 60079 standards start with two simple definition:
Area in which an explosive atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.
The term "safe area" is often used to mean non-hazardous area, it is even used in the text of some of the older standards but the term is not defined within the EN60079 range of standards. 'Safe area' could be misleading as it could be interpreted to mean relating to other potential hazards.
An area might be defined non-hazardous relating to a potentially explosive atmosphere might not be 'safe' regarding other hazards.
Area in which an explosive atmosphere is present or may be expected to be present in quantities such as to require special precautions for the construction, installation and use of electrical apparatus.
The hazardous area is also referred to as Atex Area i.e. area which the Atex Directives apply but this of course is only valid for sites within the European Union. The American term Hazloc )(Hazardous Locations) is used worldwide and becoming more prevalent in the UK, it is a perfectly good term although not defined in the EN Standards.
The hazardous area is divided in Zones dependent on the probability of an explosive atmosphere occurring.