login Login / Register
background image

How to classify Hazardous locations?

Hazardous location — An area where the possibility of explosion and fire is created by the presence of flammable gases, vapors, dust, fibers or flyings.

Class I – Gas

Class I – Class I locations are those in which flammable gases, flammable liquid-produced vapors or combustible liquid-produced vapors are or may be present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Typical class I locations:

− Petroleum refineries and gasoline storage areas

− Industrial firms that use flammable liquids in dip tanks for parts cleaning or other operations

− Petrochemical companies that manufacture chemicals from gas and oil

− Dry cleaning plants where vapors from cleaning fluids can be present

− Companies that have spraying areas where they coat products with paint or plastics − Aircraft hangars and fuel serving areas

− Utility gas plants and operations involving storage and handling of liquified petroleum gas or natural gas

Class II – Dust

Class II – Class II locations are those that are hazardous because of the presence of combustible dust.

Typical class II locations:

− Grain elevators, flour and feed mills

− Plants that manufacture, use or store magnesium or aluminum powders

− Plants that have chemical or metallurgical processes: producers of plastics, medicines and fireworks, etc.

− Producers of starch or candies

− Spice-grinding plants, sugar plants and cocoa plants

− Coal preparation plants and other carbon handling or processing areas

The following table describes a simplified comparison of the different designations for the classification of gas hazardous areas:

Allocation of gas hazardous areas and typical ignition protection typesn Class I, Division 1

Explosion proof (comparable with Ex d, but more stringent
requirement) Intrinsic safety (Ex ia)

Class I, Division 2

All Division 1 ignition
protection types

Zone 0

Ex ia“Intrinsic safety”

Zone 1

Ex d“flameproof enclosure”
Ex ib “intrinsic safety”
All Zone 0 ignition protection types

Zone 2

Ex nA“non-sparking”
All Zone 0 and Zone 1
ignition protection types

Description of hazardous areas Explosive atmosphere is
present continuously or very
frequently and over a long time
In normal operation,
explosive atmosphere
is present occasionally
In normal operation,
explosive atmosphere
is normally not present or only
for short times

Class III – Fibers

Class III – Class III locations are those that are hazardous because of the presence of easily ignitable fibers or where materials producing combustible flyings are handled, manufactured or used, but in which such fibers/flyings are not likely to be in suspension in the air in quantities sufficient to produce ignitable mixtures.

Typical class III locations:

− Textile mills, cotton gins, cotton seed mills and flax processing plants

− Any plant that shapes, pulverizes or cuts wood and creates sawdust or flyings

Note: Fibers and flyings are not likely to be suspended in the air but can collect around machinery or on lighting fixtures and a spark or hot metal can ignite them.

Division 1 – Normally hazardous

Division 1 – Hazardous gases or dusts are present under normal operation conditions or during frequent repair and maintenance activity.

Groups A, B, C, D

Groups A, B, C and D – The gases and vapors of class I locations are broken into four groups by the code A, B, C and D. These materials are grouped according to the ignition temperature of the substance, its explosion pressure and other flammable characteristics.

Groups E, F, G

Groups E, F, G – Class II dust locations groups E, F and G are classified according to the ignition temperature and the conductivity of the hazardous substance.

Division 2 – Not normally hazardous

Division 2 – Hazardous gases or dusts are not present under normal operating conditions.

If you have any questions about the various models or for Ex protection, your contact person will be pleased to assist.

Open chat
Need Help ?
Can we help you ?