Hazardous locations are classified into ZONES so as to facilitate the selection of the correct electrical apparatus and to ensure that the electrical design and installation meets the specified requirements to be used in different areas. The zone classification is based on the likelihood and the duration of an explosive atmosphere.

The zone classification for gases is divided into three zones, namely Zone 0, Zone 1 and Zone 2 and for dusts Zone 20, Zone 21 and Zone 22.

Definition of hazardous area zones (AS/NZS 60079.10):

Zone 0:

• “Place in which an explosive atmosphere consisting of a mixture with air of flammable substance in the form of gas, vapour or mist is present continuously for long periods or frequently”
• As per experts experience that a Zone 0 CONDITION is rarely encountered and is limited mainly to confined spaces (such as the vapour space of closed process vessels, closed storage tanks and closed containers), although it can occur in larger rooms, such as chemical plants. From the Institute of Petroleum (IP 15) an exposure exceeding 1000 hours per year is often used.

Zone 1:

• “Place in which an explosive atmosphere consisting of a mixture with air of flammable SUBSTANCES in the form of gas, vapour or mist is likely to occur in normal operation occasionally”
• A Zone 1 classification usually includes locations where volatile flammable liquids or liquefied flammable gasses are transferred; gas GENERATOR rooms; inadequately ventilated pump rooms for flammable gases or for volatile flammable liquids; and most other locations where hazardous concentrations of flammable vapours or gases can occur in the course of normal operations. IP 15 stipulates between 10 hours and 1000.

Zone 2:

“Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only”

Generally, for an area to be classified as a Zone 2 location the following conditions SHALL normally be regarded as the minimum requirements for the area:

1. The area is so well ventilated that if an abnormal conditions arises, ignitable concentrations of the gas or vapour are rapidly dispersed; and
2. Complete segregation from Zone 1 locations is ensured.

In this case an expose to flammable vapours or gases of less than 10 hours per annum is prescribed in IP 15.

Hazardous locations are classified into zones so as to facilitate the selection of the correct electrical apparatus and to ensure that the electrical design and installation meets the specified requirements to be used in different areas. The zone classification is based on the likelihood and the duration of an explosive atmosphere.

The zone classification for gases is divided into three zones, namely Zone 0, Zone 1 and Zone 2 and for dusts Zone 20, Zone 21 and Zone 22.

Definition of hazardous area zones (AS/NZS 60079.10):

Zone 0:

Zone 1:

Zone 2:

“Place in which an explosive atmosphere consisting of a mixture with air of flammable substances in the form of gas, vapour or mist is not likely to occur in normal operation but, if it does occur, will persist for a short period only”

Generally, for an area to be classified as a Zone 2 location the following conditions shall normally be regarded as the minimum requirements for the area:

In this case an expose to flammable vapours or gases of less than 10 hours per annum is prescribed in IP 15.