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 EN 60079 standards start with two simple definition:
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 non-hazardous, which is defined relating to a potentially explosive atmosphere, but may not be 'safe' regarding other hazards.
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 with the European Union. The American term Hazloc )(Hazardous Locations) is becoming more prevalent and 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.