Hazardous Areas Classification - Europe

European hazardous areas classifications in zones, protection types, temperature codes and codes

Hazardous areas outside North America are classified by gas groups and zones.

  • Zones are used to define the probability of the presence of flammable materials.
  • Groups classify the exact flammable nature of the material.

Protection Types are used to denote the level of safety for the device. Equipment approved receives a temperature code indicating the maximum surface temperature of the equipment.

Zones

The zone defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere.

Zone 0

Area in which an explosive gas-air mixture is continuously present or present for long periods.

Zone 1

Combustible or conductive dusts are present. Area in which an explosive gas-air mixture is likely to occur for short periods in normal operation.

Zone 2

Area in which an explosive gas-air mixture is not likely to occur, and if it occurs it will only exist for a very short time due to an abnormal condition.

Protection Types

Different protection techniques are used to address the hazardous zones.

Ex Protection Types

 

Zone

Ex d

Flameproof (Explosion proof) Enclosure

1, 2

Ex e

Increased Safety

1, 2

Ex ia

Intrinsically Safe

0, 1, 2

Ex ib

Intrinsically Safe

1, 2

Ex o

Oil Immersion

2

Ex p

Pressurized Apparatus (Purged Apparatus)

1, 2

Ex q

Powder Filling (Sand Filling)

2

Ex m

Encapsulation

1, 2

Ex n or Ex N

Non incentive or/and normally no sparking circuits

2

 

Flameproof (Explosion proof) Enclosure

All electrical circuits are enclosed in a house strong enough to contain any explosion or fire that may take place on the inside.

Increased Safety

Electrical circuits incorporates special measures to reduce the probability of excessive temperatures and the occurrence of arcs and sparks in normal service.

Intrinsically Safety

The electrical energy available in circuits and equipment, is limited to a level to low to ignite the most easily ignitable mixtures in a hazardous area.

Intrinsically safe barriers, as Zener, are installed in the circuit to limit current and voltage in the hazardous areas to avoid sparks or hot spots under fault conditions.

 

Temperature Codes

A mixture of air and hazardous gases may ignite by coming in contact with a hot surface. An ignition depends on surface area, temperature and the concentration of the gas.

Certified equipment are tested for maximum temperature ratings by approval agencies. Equipment for Group II receives a temperature code indicating the maximum surface temperature.

Temperature Code

oF

oC

T1

842

450

T2

572

300

T3

392

200

T4

275

135

T5

212

100

T6

185

85

The coding is based on a 104 oF (40 oC) ambient temperature.

The automatic ignition temperature can be found in IEC 79-4.

Groups

Electrical equipment are divided into two groups where Group I covers equipment used in mines and Group II covers all other applications. Group II is subdivided into three subgroups where the specific hazardous materials within each group can be found in CENELEC EN 50014.

Group I

For application in below ground installations (mines) where methane (firedamp) and coal dust may be present.

Group IIA

For application in above ground installation where hazards due to propane may exist.

Group IIB

For application in above ground installations where hazards due to ethylene may exist.

Group IIC

For application in above ground installations where hazards due to hydrogen or acetylene may exist.

Print Email

Hazardous Areas Classification - North America

North American hazardous locations classification in classes, divisions and groups

Electrical devices used in hazardous areas need to be certified for use according the requirements specified for the area.

In North America certification is provided by

  • Factory Mutual - An approval agency primarily concerned with insurance underwriting
  • Underwriters Laboratories  - An independent, not-for-profit product safety testing and certification organization
  • Canadian Standards Association  - A not-for-profit membership-based association serving business, industry, government and consumers in Canada developing standards addressing public safety and health

The types of protection required depends on the risk involved in the area.

In general hazardous locations in North America are separated by classes, divisions, and groups to define the level of safety required for equipment installed in these locations.

Classes

The classes defines the general nature of hazardous material in the surrounding atmosphere.

Class

Hazardous Material in Surrounding Atmosphere

Class I

Hazardous because flammable gases or vapors are present in the air in quantities sufficient to produce explosive or ignitable mixtures.

Class II

Hazardous because combustible or conductive dusts are present.

Class III

Hazardous because ignitable fibers or flying's are present, but not likely to be in suspension in sufficient quantities to produce ignitable mixtures. Typical wood chips, cotton, flax and nylon. Group classifications are not applied to this class.

Divisions

The division defines the probability of hazardous material being present in an ignitable concentration in the surrounding atmosphere.

Division

Presence of Hazardous Material

Division 1

The substance referred to by class is present during normal conditions.

Division 2

The substance referred to by class is present only in abnormal conditions, such as a container failure or system breakdown.

Groups

The group defines the hazardous material in the surrounding atmosphere.

Group

Hazardous Material in Surrounding Atmosphere

Group A

Acetylene

Group B

Hydrogen, fuel and combustible process gases containing more than 30% hydrogen by volume or gases of equivalent hazard such as butadiene, ethylene, oxide, propylene oxide and acrolein.

Group C

Carbon monoxide, ether, hydrogen sulfide, morphline, cyclopropane, ethyl and ethylene or gases of equivalent hazard.

Group D

Gasoline, acetone, ammonia, benzene, butane, cyclopropane, ethanol, hexane, methanol, methane, vinyl chloride, natural gas, naphtha, propane or gases of equivalent hazard.

Group E

Combustible metal dusts, including aluminum, magnesium and their commercial alloys or other combustible dusts whose particle size, abrasiveness and conductivity present similar hazards in connection with electrical equipment.

Group F

Carbonaceous dusts, carbon black, coal black, charcoal, coal or coke dusts that have more than 8% total entrapped volatiles or dusts that have been sesitized by other material so they present an explosion hazard.

Group G

Flour dust, grain dust, flour, starch, sugar, wood, plastic and chemicals.

The specific hazardous materials within each group and their automatic ignition temperatures can be found in Article 500 of the National Electrical Code and in NFPA 497.

Group A, B, C and D apply to class I locations. Group E, F and G apply to class II locations.

Temperature Code

A mixture of hazardous gases and air may ignite in contact with a hot surface. The condition for ignition depends on several factors as surface area, temperature and concentration of gas.

Equipment approved receives a temperature code indicating the maximum surface temperature of the equipment.

Temperature Code

Maximum Surface Temperature

oF

oC

T1

842

450

T2

572

300

T2A

536

280

T2B

500

260

T2C

446

230

T2D

419

215

T3

392

200

T3A

356

180

T3B

329

165

T3C

320

160

T4

275

135

T4A

248

120

T5

212

100

T6

185

85

Equipment that not exceed a maximum surface temperature of 212 oF (104 oF ambient temperature) is not required to be marked with a temperature code (NEC).

Print Email