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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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) |
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Flame Proof | Prevents transmission of explosion to surroundings |
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Luminaries, rotating machines, Switchgear |
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Increased Safety | Prevents arcing, sparking and hot surfaces |
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Terminal and junction boxes, lighting, rotating machines |
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Intrinsic Safety | Prevents arcing, sparking and hot surfaces by energy limitation |
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Measuring and instrumentation, fieldbus |
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Pressurised | Hazardous material isolated from ignition capable parts |
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Control panels, analysers, engines |
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Simple Pressurisation |
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Encapsulation | Hazardous material isolated from ignition capable parts, generally by use of a potting compound |
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Relays, low cost & non reparable items, engine coils/solenoids |
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Oil Immersion | Hazardous material isolated from ignition capable parts, generally by use of mineral oil |
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DCS, Transformers, relays, start up |
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Powder Filling | Prevents transmission of explosion to surroundings, generally by use of a quartz powder |
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Relays, condensers, power supplies and similar apparatus |
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ATEX Zone 2, 22 Protection Types
Ex Marking Code | Protection principle | Definintion | Application | ATEX/CENELEC /IEC | Possible use | Equipment protection level (EPL) |
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Non incendive | Not capable of causing ignition in normal operation |
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Luminaries, low power equipment, rotating machines, fuses |
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Restricted Breathing | Keep out hazardous material by means of adequate sealing (IP66) |
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Arcing sparking and hot surfaces, inverters, control & inst components, actuators, relays, PLC’s |
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Non Sparking | Not capable of causing ignition in normal operation |
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Fuses, Shunts, restistors, low power equipment, transformers, batteries |
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Energy Limited | Power insufficient to cause ignition |
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Lower power PCB, PLC’s |
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Enclosed break | No transmisson to surroundings. |
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Switch gear (closed), reduced spec Ex d, reduced encapsulation “m” for circuits |
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Non Incendive | As above. | |||||
Hermetically sealed | Primary sparking device is fusion sealed. | |||||
Simple encapsulation | Potting compound used. | |||||
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Pressurised | Keep out hazardous material by positive internal pressure and adequate sealing |
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Renders internal Ignition capable components (high grade industrial or Zone 2 ATEX EC type quality) suitable for non-hazardous area |
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Simple Pressurisation | As above |
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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

Apparatus “X” Certificate

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