Electrical equipment used in locations where explosion and fire hazards could potentially exist because of the presence of combustible dusts, flammable liquids, gases and vapors, or ignitable flyings and fibers, must conform to standards as set forth in the National Electrical Code in order to protect against these hazards. Any equipment which is powered through the use of electrical current or creates heat or sparks through its operation holds the potential to ignited flammable materials and atmospheres and must be designed to prevent such ignition. Although there are several common techniques used in designing equipment for use in hazardous locations, each has the same goal of maintaining compliance with a certain set of classifications. Despite the variance in designs, all equipment intended for use in hazardous locations falls under either the “intrinsically safe” designation or the “explosion proof” designation.
Locations are designated according to a host of factors including the types of materials to be encountered, the nature of the location (confined, open, etc) and the likelihood of the presence of flammable materials. As an example, Class 1 Division 1 locations represent areas where highly flammable gases and vapors (class 1) are present on a regular basis as a part of normal operations (division 1). Class 1 denotes the types of flammable materials encountered and Division 1 denotes the likelihood of their presence. Thus, a Class 1 Division 2 locations denotes the same gases and vapors (class 1), but with their presence being only on an infrequent or abnormal basis (division 2).
Regardless of a locations class and division designation, if it is classified as a hazardous location, the potential for fire or explosion is considered to always be present. Although the possibility of ignition may vary according to class and division, this does not reduce the severity of the threat posed by ignition. As a result, any location designated as hazardous must employ the use of the appropriately classed equipment in order to maintain compliance with the National Electrical Code as well as federal and local regulations.
Explosion proof equipment is the most common type of NEC compliant equipment in use. This type of equipment covers a wide range of power levels and is most commonly designed to prevent ignition through the use of special housings intended to contain explosions or ignitions of flammable materials within the housings long enough to allow them to cool below ignition temperatures before exiting the housing. Intrinsically sage equipment is less common and has a much narrower scope of application. Intrinsically safe equipment is usually completely sealed against intrusion from the outside atmosphere and designed to use very low voltage, thus making it incapable of producing enough heat to create heat, sparks or flame that could cause ignitions.
Class 1 Division 2 equipment falls within the explosion proof designation as the extreme protection levels of intrinsically safe approval are not necessary to achieve sufficient protection in Class 1 Division 2 locations. Class 1 Division 2 equipment is designed to protect against occasional exposure to flammable compounds and materials under abnormal conditions such as leaks or spills. Class 1 Div 2 equipment is not suitable for confined locations or areas where flammable materials are present on a regular basis. Class 1 Division 2 equipment is typically used in large open areas such as manufacturing and processing plants to provide protection against possible exposure to flammable compounds while producing good general area illumination.
It should be noted that although Class 1 Division 2 equipment is not intended for the acute hazardous conditions represented by Class 1 Division 1 locations, the importance of the protection it provides is no less critical. Although the potential for explosion or fire may not be as likely, the severity of such ignitions can be no less deadly than any other class. This makes it critical that any equipment chosen for use in Class 1 Division 2 locations be of the highest quality possible. Additionally, such equipment must carry proof of approval from a certified testing agency such as UL or CSA. It is only through the proper use and application of correctly certified equipment that effective protection is ensured regardless of the level of fire or explosion potential implied by a locations’ classification.