Hazardous Areas Explained

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What is a Hazardous Area?

  • A hazardous area is a location which either has or may have an explosive concentration of gas, vapour or dust.
  • The more often the flammable substance is present, the more hazardous the area is.
  • An area that has the presence of flammable gas. Hazardous areas are divided into the following:-
    Zone 0: > 1000 hours /year
    Zone 1: 10 to 1000 hours/year
    Zone 2: < 10 hours/year

Dust explosion pentagon

Example of hazardous area zones

Building a Certificate Label

  • Marking and meaning for Electro-Technical Equipment/ Apparatus
  • Certified according to CENELEC Standard

Gas protection

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Gas-Protection

Dust protection

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ATEX Zone 0, 20, 1, 21 Protection Types

Ex Marking Code Protection principle Definition Application Standard Possible use Equipment protection level (EPL)
  • Ex d
 Flame Proof Prevents transmission of explosion to surroundings
  • Zone 1, 2, 21, 22
  • Category 2 GD
  • IEC 60079-1
  • CENELEC-EN 50018
 Luminaries, rotating machines, Switchgear
  • Gb, Db
  • Ex e
 Increased Safety Prevents arcing, sparking and hot surfaces
  • Zone 1, 2
  • Zone 21, 22
  • Category 2 GD
  • IEC 60079-7
  • CENELEC- EN 50019
 Terminal and junction boxes, lighting, rotating machines
  • Gb, Db
  • Ex i
  • Ex ia
  • Ex ib
  • Ex ic
 Intrinsic Safety Prevents arcing, sparking and hot surfaces by energy limitation
  • Zone 0, 1, 2
  • Zone 20, 21, 22
  • Category 1 GD
  • IEC 60079-11,25,26,27
  • CENELEC-EN 50020,39
  • CENELEC-EN 50284
 Measuring and instrumentation, fieldbus
  • Ga, Gb, Gc
  • Da, Db, Dc
  • Ex p
  • Ex px
  • Ex py
  • Ex pz
 Pressurised Hazardous material isolated from ignition capable parts
  • Zone 1, 2
  • Zone 21, 22
  • Category 2 GD
  • IEC 60079-2
  • CENELEC-EN 60079-2
 Control panels, analysers, engines
  • Gb, Gc, Db, Dc
  • Gb, Gc, Db, Dc
  • Gc, Dc
  • Ex nZ
 Simple Pressurisation
  • Zone 2, 22
  • IEC 60079-15
  • Gc, Dc
  • Ex m
 Encapsulation Hazardous material isolated from ignition capable parts, generally by use of a potting compound
  • Zone 1, 2
  • Zone 21, 22
  • Category 2 GD
  • IEC 60079-18
  • CENELEC-EN 60079-18
 Relays, low cost & non reparable items, engine coils/solenoids
  • Gb, Gc
  • Db, Dc
  • Ex o
 Oil Immersion Hazardous material isolated from ignition capable parts, generally by use of mineral oil
  • Zone 1, 2
  • Zone 21, 22
  • Category 2 GD
  • IEC 60079-6
  • CENELEC-EN50015
 DCS, Transformers, relays, start up
  • Gb, Gc
  • Db, Dc
  • Ex q
 Powder Filling Prevents transmission of explosion to surroundings, generally by use of a quartz powder
  • Zone 1, 2
  • Zone 21, 22
  • Category 2 GD
  • IEC 60079-5
  • CENELEC EN 50017 & EN 60079-5
 Relays, condensers, power supplies and similar apparatus
  • Gb, Gc
  • Db, Dc

ATEX Zone 2, 22 Protection Types

Ex Marking Code Protection principle Definintion Application ATEX/CENELEC /IEC Possible use Equipment protection level (EPL)
  • Ex n/ N
 Non incendive Not capable of causing ignition in normal operation
  • Zone 2, 22 or
    non hazardous area
  • Category 3 GD
  • 60079-15
  • EN 50021
 Luminaries, low power equipment, rotating machines, fuses
  • Gc
  • Ex nR
 Restricted Breathing Keep out hazardous material by means of adequate sealing (IP66)
  • Zone 2, 22 or
    non hazardous area
  • Category 3 GD
  • 60079-15
  • EN 50021
 Arcing sparking and hot surfaces, inverters, control & inst components, actuators, relays, PLC’s
  • Gc
  • Ex nA
 Non Sparking Not capable of causing ignition in normal operation
  • Zone 2, 22 or
    non hazardous area
  • Category 3 GD
  • 60079-15
  • EN 50021
 Fuses, Shunts, restistors, low power equipment, transformers, batteries
  • Gc
  • Ex nL
 Energy Limited Power insufficient to cause ignition
  • Zone 2, 22 or
    non hazardous area
  • Category 3 GD
  • 60079-15
  • EN 50021
 Lower power PCB, PLC’s
  • Gc
  • Ex nC
 Enclosed break No transmisson to surroundings.
  • Zone 2, 22 or
    non hazardous area
  • Category 3 GD
  • 60079-15
  • EN 50021
 Switch gear (closed), reduced spec Ex d, reduced encapsulation “m” for circuits
  • Gc
Non Incendive As above.
Hermetically sealed Primary sparking device is fusion sealed.
Simple encapsulation Potting compound used.
  • Ex pZ
 Pressurised Keep out hazardous material by positive internal pressure and adequate sealing
  • Zone 2, 22
  • IEC 60079-15
 Renders internal Ignition capable components (high grade industrial or Zone 2 ATEX EC type quality) suitable for non-hazardous area
  • Gc
  • Ex nZ
 Simple Pressurisation As above
  • Zone 2, 22
  • IEC 60079-15
  • Gc

Comparison of IEC and North American Terminology

Although USA & Canada are IEC members, NA terminology relating to hazardous atmospheres may still be encountered. A comparison of the 2 systems are as such

IEC Zone NA Division
0 1
1
2 2
Class Group Gas/Vapour
I A Acetylene
B Hydrogen
C Ethylene
D Propane
II Dusts
E Metal
F Carbonaceous
G Non conductive
III Fibres Linters
No sub groups

Certification Labels

Component “U” certificate
iTB Range Enclosure
Apparatus “X” Certificate
Apparatus-X-Certificate02

Ingress protection

  • IP ratings give protection from solid objects (IP6X) and water (IPX6)
  • The minimum IP rating for Ex e is IP54
  • indEx enclosures are IP66 as standard
  • IP66 most onerous test – dust tight and protection from powerful water jets
  • IP67 and IP68 on request

Find out more about IP67, 68