Hazardous Area Classifications
Standards used in North America.
Hazardous (classified) locations in accordance with Article 500, National Electrical Code
Example:
Permitted Class
Permitted Division
Permitted Group
Temperature Class
Class I Div 2 Group A, B, C & D T3
Permitted Class
Class I: Combustible material in the form of a gas vapor.
Class II: Combustible material in the form of a dust.
Class III: Combustible material in the form of a fiber, such as textile flyings.
Permitted Group
The Group sub-divides the Class and describes atmospheres containing:
Group A: acetylene.
Group B: hydrogen, gases or vapors of equivalent hazards, such as manufactured gas.
Permitted Division
The Division defines the probability of an explosive mixture being present (e.g. a hazardous mixture is normally present in a Division 1 area but will only be present accidentally in a Division 2 area).
Division 1: Places where ignitable concentrations of flammable gases or vapors exist under normal conditions or may frequently exist either because of maintenance operations or where malfunctions may release ignitable vapors and simultaneously cause failure of electrical equipment.
Division 2: Locations where flammable liquids or gases are present but are normally contained and can escape only through accident or abnormal operation. Also included are areas made safe by mechanical ventilation but might become hazardous because of failure or abnormal operation of the equipment. A third Division 2 situation is an area adjacent to a Division 1 location where ignitable concentrations of gas or vapour might occasionally be communicated.
Group C: ethyl ether vapors, ethylene of cyclopropane.
Group D: gasoline, hexane, naphtha, benzene, butane, propane, alcohol, acetone, benzol, lacquer, solvent vapors or natural gas
Group E: metal dust including magnesium and its commercial alloys and other metals with similarly hazardous characteristics.
Group F:
Group G: carbon black coal or coke dust.
flour, starch or grain dust.
Temperature Class
T1: 450°C (842°F)
T2: 300°C (572°F)
T3: 200°C (392°F)
T4: 135°C (275°F)
T5: 100°C (212°F)
T6: 85°C (185°F)
Equipment may be exposed to gases with a higher ignition temperature than this value.
Advisory note
This document provides a simplified overview of the background to hazardous area classifications and is believed to be correct at the time of publication.
The National Electrical Code (NEC) is published by the National Fire Protection
Agency (NFPA). For further information please visit www.nfpa.org
and view codes and standards.
Copyright © Westlock. All rights reserved WESBUL-09075-US-1301

Hazardous Area Classifications
Standards used Internationally and in Europe
Hazardous (classified) locations in accordance with IEC and EU (European) standards
The IEC (International Electrotechnical Commission) classifications as per IEC 60079 -10 are as follows:
Example:
Explosion protection
Ex ia IIC
Type of protection
Gas Group classification
Temperature classification
T4
Type of protection Gas Group classification d: flameproof enclosure - contain explosion and quench flame p: pressurized enclosure - fill with inert gas ia: intrinsically safe for Zone 0 - limit energy ib: Intrinsically safe for Zone 1 - limit energy o: oil immersion s: special protection e: increased safety - no arcing, sparking or hot surfaces m: encapsulation - sealed arcing devices or non-arcing q: sand-filled nL: nonincendive - limited energy nA: nonincendive - non sparking me: encapsulation/increased safety
The Group describes atmospheres containing:
IIC:
IIB:
acetylene and hydrogen
diethyl ether, ethylene, cyclopropane and others
IIA: gasoline, hexane, butane, naphtha propane, isoprene and many others
Temperature classification
T1: 450°C (842°F)
T2: 300°C (572°F)
T3: 200°C (392°F)
T4: 135°C (275°F)
T5: 100°C (212°F)
T6: 85°C (185°F)
Advisory note
This document provides a simplified overview of the background to hazardous area classifications and is believed to be correct at the time of publication.
Equipment may be exposed to gases with a higher ignition temperature than this value.
The IEC has a website dedicated to the IECEx system. For further information please visit www.iecex.com
.
ATEX marking (94/9/EC)
The ATEX directive consists of two EU directives describing what equipment and work environment is allowed in an environment with an explosive atmosphere. Employers must classify into zones those areas where hazardous explosive atmospheres may occur. All equipment used within European member countries must meet the ATEX hazardous and essential health and safety requirements for acceptance.
Example: II 1 G
European Community explosion protection symbol
Equipment group
Category
Explosive atmosphere
Equipment group
I: mines
II: other than mines
Category
1: Zone 0 (gas); Zone 20 (dust)
2: Zone 1 (gas); Zone 21 (dust)
3: Zone 2 (gas); Zone 22 (dust)
Explosive atmosphere
G: gases/vapors
D: dusts
Copyright © Westlock. All rights reserved Page 2

Hazardous Area Classifications
The ATEX markings are in addition to the standard zone markings and indicate compliance to the new directives. The classification given to a particular zone, its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does.
Area
Equipment group II
(surface)
Category of equipment
1
2
3
Presence or duration of explosive atmosphere
Continuous presence
Long periods
Frequent
Likely to occur
Unlikely to occur
Present for a short period
Inflammable substances
Gas, vapors, mist, dust
Gas, vapors, mist, dust
Gas, vapors, mist, dust
Level of protection
Faults to allow for
Very high level of
2 types of protection or 2 independent faults
High level of
1 type of protection:
Habitual frequent malfunction
Normal protection:
Required level of protection
Comparison with previous practice
Group II
Zone 0 (gas)
Zone 20 (dust)
Group II
Zone 1 (gas)
Zone 21 (dust)
Group II
Zone 2 (gas)
Zone 22 (dust)
Advisory note
This document provides a simplified overview of the background to hazardous area classifications and is believed to be correct at the time of publication.
For further information on the ATEX Directive please visit the European Commission website at: ec.europa.eu/enterprise/ sectors/mechanical .
A comparison between North American and European classifications is:
IEC/EU
US NEC 500
Flammable material present continuously
Zone 0
(Zone 20-dust)
Division 1
Flammable material present intermittently
Zone1
(Zone 21-dust)
IEC classification per IEC 60079-10
EU classification per EN 60079-10
US classification per ANSI/NFPA 70 National Electric Code (NEC) Article 500
Flammable material present abnormally
Zone 2
(Zone 22-dust)
Division 2
US/Canada: Saddle Brook, NJ
Ph: +1 201 794 7650
Fax: +1 201 794 0913
E-mail: westlockinfo@westlockcontrols.com
South America: Sao Paulo, Brazil
Ph: +55 11 2588 1400
Fax: +55 11 2588 1410
E-mail: comercial@westlock.com.br
Copyright © Westlock. All rights reserved
Europe: Kent, England
Ph: +44 1892 516277
Fax: +44 1892 707620
E-mail: sales@westlockuk.com
Asia: Singapore
Ph: +65 6768 5850
E-mail: sales@westlockuk.com
Page 3