This section provides a useful reference source for visitors to our site. Here you will find details of certification standards as well as definitions of hazardous areas and explosion protection techniques.
Expo’s products are certified to all leading international standards. In North America, we have certification to NFPA 496 through cUL / ULus and FM. In Europe we are certified to the ATEX / EN standards and for Global applications we have IECEx and INMETRO certification to the IEC standards. The certification is based on a series of standards -Electrical Equipment for Use in explosive Atmospheres.
Hazardous areas are locations where the potential for fire or explosion exists because of gases, dust, or easily ignitable fibers or filings in the atmosphere.
In North America, hazardous areas are separated by classes, divisions, and groups to define the level of safety required for equipment installed in these locations. Classes define the general form of the flammable materials in the atmosphere. Divisions define the probability of the presence of flammable materials. Groups classify the exact flammable nature of the material. In 1998 Canada introduced the “Zone” system for new hazardous area plants.
In Europe and countries outside of USA, classification of hazardous areas is accomplished differently. Zones are used to define the probability of the presence of flammable materials. Protection Types denote the level of safety for the device. Groups classify the exact flammable nature of the material. These groups are separated differently than USA Groups. Temperature identifications convey the maximum surface temperature of the apparatus based on 104° F (40° C) ambient. These temperature codes are selected carefully not to exceed the ignition temperature of the specific gas or vapor to be encountered in the application.
Explosion Protection Techniques
To enable electrical equipment to be used in hazardous areas, eight commonly recognized explosion-protection techniques have been developed over the years. National or international standards and codes of practice govern each technique and define in detail how the equipment should be designed and applied. National certifying (or approvals) authorities ensure design compliance and national inspectorates (or insurance companies) vet and usually inspect each installation.
Flameproof [Ex d]
IEC/European Harmonized Standard 60079-1
A method of protection where the equipment is contained within an enclosure, which will withstand an internal explosion of a flammable gas or vapor that may enter it, without suffering damage and without communicating the internal flammation to the external explosive atmosphere through any joints or structural openings in the enclosure. The enclosure will be designed for a particular gas grouping (I, IIA, IIB or IIC). This design concept is reflected in the equipment marking by the symbol ‘Ex d’. Equipment designed to this concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Intrinsic Safety – Apparatus [Ex ia] or System [Ex ib]
IEC/European Harmonized Standard 60079-11
A protection technique based upon the restriction of electrical energy within the apparatus and in the interconnecting wiring,
exposed to an explosive atmosphere, to a level below that which can cause ignition by either sparking or heating effects. Because of the method by which intrinsic safety is achieved, it is necessary that not only the electrical apparatus exposed to the explosive atmosphere, but also other (associated) electrical apparatus with which it is interconnected, is suitably constructed. The concept is divided into two sub-types which are dependent upon the number of allowable fault conditions. The symbols ‘ia’ and ‘ib’ denote the sub-types. This design concept is reflected in the equipment marking by the symbols ‘Ex ia’ or ‘Ex ib’. Equipment designed to the Ex ia concept is suitable for use in ‘Zone 0′, ‘Zone 1′ and ‘Zone 2′ hazardous areas. Equipment designed to the Ex ib concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Pressurization [Ex p]
IEC/European Harmonized Standard 60079-2
A method of protection using the pressure of a protective gas to prevent the ingress of an explosive atmosphere to a space that may contain a source of ignition and, where necessary, using continuous dilution of an atmosphere within the space that contains a source of emission gas, which may form an explosive atmosphere. This design concept is reflected in the equipment marking by the symbol ‘Ex p’. Equipment designed to this concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Increased safety [Ex e]
IEC/European Harmonized Standard 60079-7
A method of protection by which additional measures are applied to electrical apparatus to give increased security against the possibility of excessive temperatures and of the occurrence of arcs and sparks during the life of the apparatus. It applies only to electrical apparatus, no parts of which produce sparks or arcs, or exceeds the limiting temperature of the materials upon which safety depends that are used in its construction. This design concept is reflected in the equipment marking by the symbol ‘Ex e’. Equipment designed to this concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Oil immersion [Ex o]
IEC/European Harmonized Standard 60079-6
A method of protection where the electrical apparatus is made safe by oil immersion whereby an explosive atmosphere above the oil or outside the enclosure will not be ignited. The oil presents a barrier between the explosive atmosphere and the electrical apparatus. This design concept is reflected in the equipment marking by the symbol ‘Ex o’. Equipment designed to this concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Powder filling (sand filling) [Ex q]
IEC/European Harmonized Standard 60079-5
A method of protection where the enclosure of the electrical apparatus is filled with a mass of granular material such that if an arc occurs, the arc will not be liable to ignite the external explosive atmosphere. This design concept is reflected in the equipment marking by the symbol ‘Ex q’. Equipment designed to this concept is suitable for use in ‘Zone 1′ and ‘Zone 2′ hazardous areas.
Encapsulation [Ex m]
IEC/European Harmonized Standard 60079-18
A type of protection in which parts that could ignite an explosive atmosphere by either sparking or heating are enclosed in a compound in such a way that the explosive atmosphere cannot be ignited. The compound provides a barrier between the electrical apparatus and the explosive atmosphere. This design concept is reflected in the equipment marking by the symbol ‘Ex m’. There are different levels of Ex m, “Ex ma” for equipment designed to this concept, suitable for Zone 0 and “Ex mb” for equipment designed to this concept, suitable for Zone 1.
Type N protection (normally non-sparking and/or non-incendive circuits) [Ex n]
IEC/European Harmonized Standard 60079-15
A type of protection applied to electrical apparatus such that, in normal operation, it is not capable of igniting a surrounding explosive atmosphere, and a fault capable of causing ignition is not likely to occur. This design concept is reflected in the equipment marking by the symbol ‘Ex n’. There are four types of Ex n, Ex nA for Non-Sparking apparatus, Ex nC for Non-incendive, sealed, encapsulated apparatus, Ex nL for Energy Limited apparatus and Ex nR for Restrictive Breathing apparatus. Equipment designed to this concept is suitable for use in ‘Zone 2′ hazardous areas.
In North America, hazardous areas are separated by Classes, Divisions and Groups to define the level of safety required for equipment installed in these locations.
Classes define the general form of the flammable materials in the atmosphere:
|Class I||Flammable gases or vapors are present in the air in quantities sufficient to produce explosive or ignitable mixtures.|
|Class II||Combustible or conductive dusts are present.|
|Class III||Ignitable fibers or filings are
present, but not likely to be in suspension in sufficient quantities
to produce ignitable mixtures. (Group classifications are not applied
to this class.)
Divisions define the probability of the presence of flammable materials:
|Division I||The substance referred to by class is present during normal conditions.|
|Division II||The substance referred to by class is present only in abnormal conditions, such as a container failure or system breakdown.|
Groups classify the exact flammable nature of the material:
|Group B||Hydrogen (or gases of equivalent hazard)|
|Group C||Ethylene (or gases of equivalent hazard)|
|Group D||Gasoline (or gases of equivalent hazard)|
|Group E||Metal Dust|
|Group F||Coal Dust|
|Group G||Grain Dust|
Apparatus Temperature classification (T class)
|Maximum surface temperature||Temperature class|
|450°C (842 F)||T1|
|300°C (572 F)||T2|
|280°C (536 F)||T2A|
|260°C (500 F)||T2B|
|230°C (446 F)||T2C|
|215°C (419 F)||T2D|
|200°C (392 F)||T3|
|180°C (356 F)||T3A|
|165°C (329 F)||T3B|
|160°C (320 F)||T3C|
|135°C (275 F)||T4|
|120°C (248 F)||T4A|
|100°C (212 F)||T5|
|85°C (185 F)||T6|
North America Hazardous Location Information
Europe / IEC
In Europe and IEC countries, hazardous areas are classified by Zones,
Protection Types, Groups and Temperature Classes.
Industrial plants are zoned according to the likelihood of a potentially explosive atmosphere being present
|Zone 0 (gases)
Zone 20 (dusts)
|Flammable material present continuously or for long periods (typically 1000 hours or more per year)|
|Zone 1 (gases)
Zone 21 (dusts)
|Flammable material present in normal operation (typically between 10 and 1000 hours per year)|
|Zone 2 (gases)
Zone 22 (dusts)
|Flammable material present in abnormal conditions only (typically less than 10 hours per year)|
|Typical gas hazard||
EUROPEAN EN 60079-0
Apparatus temperature classification (T class)
|Maximum surface temperature||IEC/EUROPEAN Temperature class|
Protection Methods & Standards for Group II Electrical Apparatus for gas atmospheres
|EN / IEC||Permitted
|Zone 0||Zone 1||Zone 2|
|General Requirements||60079-0||Basic electrical & mechanical requirements|
|Oil Immersion||o||2||60079-6||Yes||Yes||Transformers, starting resistors|
|Pressurized||p||2||60079-2||Yes||Yes||Switchgear and control cabinets, analyzers,
|Powder filled||q||2||60079-5||Yes||Yes||Transformers, capacitors, heating conductor
|Flameproof||d||2||60079-1||Yes||Yes||Switchgear and controlgear, indicating
equipment, transformers, light fittings, motors, heating equipment
|Increased safety||e||2||60079-7||Yes||Yes||Terminal & connection boxes|
|ia||1||60079-11||Yes||Yes||Yes||Safe with 2 faults. Level measurement|
|ib||2||60079-11||Yes||Yes||Safe with 1 fault. Instrumentation and
communication technology, sensors, actuators
|Encapsulated||m||2||60079-18||Yes||Yes||Solenoid valves. low power switchgear,
|Type of protection
|n||3||60079-15||Yes||Type of protection includes several
methods of ignition protection