Comparison between the Class, Division System and the Zone System

The evolution of hazardous location electrical codes and standards throughout the world has taken two distinct paths.
 
In North America, a “Class, Division” System has been used for decades as the basis for area classification of hazardous (classified) locations. Because the hazards and methods of protecting
electrical equipment against these hazards differ for different materials, hazardous locations are divided into three Classes, and two Divisions.
 
In other parts of the world, areas containing potentially explosive atmospheres are dealt with using a “Zone System”. Zones are based predominately on the International Electro technical Commission (IEC) and the European Committee for Electro technical Standardization (CENELEC) standards.
 
The table below provides a comparison between the “Class, Division” System and the “Zone” System.
 

 
The frequency of occurance determines the level of hazard for a location, the longer the material is present, the greater the risk.

 
The following chart illustrates the differences between the various Zones.
 

 
The illustration below compares the Division and Zone systems in terms of risk assessment.