1999, all references to the zone concept of

Photo 3. Battery Operated Intrinsic Safety (IS) Gas Detector
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cannot be ignited by the electrical arcing parts withinthe oil.
6. Increased Safety (Type “e”) Equipment
Increased safety (Type “e”) equipment is a type of protection applied to electrical equipment that doesnot produce arcs or sparks during normal operationand under certain abnormal conditions. This equip-ment has additional security against the possibility of excessive temperature and the equipment is assembled very carefully to ensure that arcing or sparking frompart to part or connection to connection will not oc-cur. The increased safety concept is often combined with flameproof and other protection techniques at thetermination point outside of the enclosure to permit aconnection point.
7. Encapsulation (Type “m”) Equipment
Encapsulation (Type “m”) equipment is a type in which any parts that could cause ignition of an explo-sive atmosphere by either excessive temperature or by arcing or sparking has been encapsulated in a com-pound of some sort. This encapsulation will preventthe flammable or combustible material from migratinginto the enclosure in a large enough volume to forman ignitable atmosphere at the point of excessive tem-perature or electrical arc within the equipment.
8. Powder Filling (Type “q”) Equipment
Similar to encapsulation equipment, powder filling(Type “q”) equipment protection incorporates a quartzor glass powder as a filling material. This method sur-rounds the hot or arcing electrical parts and doesn’tpermit the ignition of the gas or vapor at a point either inside or outside the equipment enclosure.
Special Precaution with Zone Equipmentand Area Classification
The proper use and maintenance of zone equipment
Photo 6. Close Up of Increased Safety Equipment TerminalsPhoto 7. Control Station Protection Method “edm” Increased SafetyEnclosure with Flameproof Switches and Enscapsulated Indicating LightPhoto 4. Open View of Control StationPhoto 5. Close Up Shot of Control Station
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is as critical as the ability to properly classify the areafor the electrical installation for the facility. It is impor-tant that all personnel involved in the design, installa-tion, maintenance, and inspection of zone areas be very familiar with the zone concept.If abnormally low temperatures are encountered atthe installation, such as below -20°C (-4°F), specialequipment may need to be installed. If these low tem-peratures are encountered, it should be noted thatmany liquids are well below their flash points and areno longer a hazardous concentration issue; however,low temperature may also adversely affect the equip-ment operation, unless the equipment has been de-signed to operate in extremely low temperatures.For Class I, Zone 0, 1, and 2 areas,
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1996, 1999,and 2002 require classification of areas, selection of equipment, and selection of wiring methods to behandled under the supervision of a qualified, registeredprofessional engineer. The use of a qualified, registeredprofessional engineer for these systems should helpensure a degree of accountability for the installationand will remain a requirement until a significant num-ber of trained personnel familiar with the equipmentdesign and installation are available.Care should be taken where an installation that hasboth division and zone locations exists at the same fa-cility. There may be some applications where the zonesystem is located adjacent to an existing division area,and this may require different area classification meth-ods for the same plant or facility. This dual classifica-tion of a facility is acceptable; however, there are cer-tain cautions that the user must observe. Class I, Zone0 and Zone 1 locations must not abut or overlap any Class I, Division 1 or 2 locations. It is permissible tohave Class I, Division 2 and Class I, Zone 2 areas thatare adjacent to each other.Dual classification permits these two different clas-sification methods with their different wiring methodsto exist at a single facility but to provide a clear line of delineation between the two different systems. A user could reclassify a Class I, Division 1 or Division 2 areaas a Class I, Zone 0, Zone 1 or Zone 2 area provided allof the reclassified space is classified using a single flam-mable gas or vapor source.
Grouping and Classification of AreasBased on the Chemicals Used.
For the purposes of testing and approval of the electri-cal equipment suitable for the zone area and to help inarea classification of the location itself, air mixtures thathave not been oxygen enriched have been classifiedinto three groups. The three group classifications for zone applications are based upon the maximum ex-perimental safe gap (MESG) or the minimum ignitingcurrent (MIC) ratio or both. The MIC ratio is basedupon the use of methane gas as a base for comparisonto the other gases in question.These group classifications are subdivided intoGroups IIC, IIB, and IIA according to the nature of thegas or vapor and the type of protection technique. Pro-tection techniques, such as increased safety “e”, encap-sulation “m”, purged and pressurized “p”, and pow-der filled “q” equipment, are not dependent upon theignition properties of the gases in the group. Their in-herent designs will preclude the gases or vapors fromentering the enclosures or being ignited by an arcingor hot electrical part.Group IIC is an atmosphere containing acetylene,hydrogen, or flammable gas, flammable liquid-pro-duced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode when ignited,having either an MESG less than or equal to 0.50 mmor an MIC ratio less than or equal to 0.45.Group IIB is an atmosphere containing acetaldehyde,ethylene, or flammable gas, flammable liquid-produced vapor, or combustible liquid-produced vapor mixed with air that may burn or explode when ignited, hav-ing either an MESG greater than 0.50 mm and less thanor equal to 0.90 mm or an MIC ratio greater than 0.45and less than or equal to 0.80.Group IIA is an atmosphere containing acetone,ammonia, ethyl alcohol, gasoline, methane, propane,or flammable gas, flammable liquid-produced vapor,or combustible liquid-produced vapor mixed with air that may burn or explode when ignited, having either an MESG greater than 0.90 mm or an MIC ratio greater than 0.80.Equipment can be listed for the specific gas or va-por, specific mixtures of gases or vapors, or any spe-cific combination of gases or vapors. This permits elec-