In Europe and most of the world outside North America hazardous areas are classified with the Zone system - where
- Zones - defines the general nature (or properties) of the hazardous material - if its gas or dust, and the probability of the hazardous material in the surrounding atmosphere
- Groups - defines the type of the hazardous material and (partly) the location of the surrounding atmosphere
The Zone area classification system is based on the International Electrotechnical Commission
IEC 60079 Explosive atmospheres.
In North America hazardous areas are classified by the Class/Division system - or by a Zone system adapted to the IEC standards.
Zones
A Zone defines the
general nature - if it is a gas or dust - and the
probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere. The Zone system has three levels of hazard for gas or dust.
Gases, Vapors and Mists
IEC 60079-10.1 Classification of areas - Explosive gas atmospheres
| Zone | Nature and Probability of Hazard Material |
|---|
| Zone 0 | Ignitable concentrations of flammable gases or vapors which are present continuously or for long periods of time. |
| Zone 1 | Ignitable concentrations of flammable gases or vapors which are likely to occur under normal operating conditions. |
| Zone 2 | Ignitable concentrations of flammable gases or vapors which are not likely to occur under normal operating conditions and do so only for a short period of time. |
Dusts
IEC 60079-10.2 Classification of areas - Combustible dust atmospheres
| Zone | Nature and Probability of Hazard Material |
|---|
| Zone 20 | An area where combustible dusts or ignitable fibers and flyings are present continuously or for long periods of time. |
| Zone 21 | An area where combustible dusts or ignitable fibers and flyings are likely to occur under normal operating conditions. |
| Zone 22 | An area where combustible dusts or ignitable fibers and flyings are not likely to occur under normal operating conditions and do so only for a short period of time. |
Zones compares to classes and divisions in the North American
Class/Division system.
Group
Group define the
type of hazardous material and (partly) the
location of the surrounding atmosphere. Group is divided in three groups where group I is reserved for mining locations.
| Group | Type of Hazardous Material and Location of Atmosphere |
|---|
| Group I |
| Mines
susceptible to firedamp (flammable mixture of gases naturally occurring in a mine). |
| Group II |
| Explosive gas atmosphere other than mines susceptible to firedamp. Group II equipment is subdivided into three subgroups. |
| A | Atmospheres containing propane, acetone, benzene, butane, methane, petrol, hexane, paint solvents or gases and vapors of equivalent hazard. |
| B | Atmospheres containing ethylene, propylene oxide, ethylene oxide, butadiene, cyclopropane, ethyl ether, or gases and vapors of equivalent hazard. |
| C | Atmospheres containing acetylene, hydrogen, carbon disulphide or gases and vapors of equivalent hazard. |
| Group III |
| Explosive dust
atmosphere. Group III equipment is subdivided into three subgroups. |
| A | Atmospheres containing combustible flyings. |
| B | Atmospheres containing non-conductive dust. |
| C | Atmospheres containing conductive dust. |
Example - Hazardous Area Classification
A room with a propane gas installation will typically be classified as
A petrol pump will typically be classified as