Industrial and commercial work areas where flammable chemicals, materials, vapors, gases or other materials such as combustible dusts are present, or operations create the potential for fires or explosions, are typically considered hazardous locations by regulating bodies such as OSHA. Such hazardous locations are required by laws and regulating agencies to institute and implement procedures and equipment that is capable of reducing or eliminating the potential for fires or explosions these locations present.   

Practicing prevention and providing protection in hazardous locations is accomplished in several ways. Prevention is primarily accomplished through providing training and instilling procedures at the worker level intended to establish safe practices when handling or working with flammable materials or within hazardous locations. Protection is provided through the inclusion of equipment that has been approved by accepted laboratories such as UL as being either intrinsically safe or explosion proof.

Intrinsically safe equipment is at its core designed to operate with a limited current level that is kept below a point where it could potentially produce ignition through the creation of heat, sparks or flame. Such equipment is generally of the highest approval rating and suitable for a wide variety of hazardous environments, but as will all explosion proof equipment, specific suitability is determined by classification and rating.

Explosion proof equipment is generally equipment that prevents ignition by either completely sealing all possible sources of ignition from contact with potentially flammable compounds or materials within a housing that can withstand fire or explosion and keep internal combustion from exiting the housing, or restricting the exit of heated gases to slow their exit enough so they are too cool to ignite the surrounding atmosphere once they leave the fixture.

Regardless of how protection is achieved, all electrical equipment used in hazardous locations must be rated for use in that particular type of environment. Determination is made through the use of a rating system outlined in the National Electrical code which is made up of classes, divisions, groups, and or zones. Classes designate the type of hazardous materials that may be encountered and include Class 1 for vapors and gases, Class 2 for combustible dusts, and Class 3 for Fibers and Flyings. Divisions designate the typical conditions of the hazardous location and are based on whether the hazard will exist as a normal part of operations (Division 1-Normal)or has the potential to exist but is not normally encountered all the time (Division2-abnormal).

 Groups designate the nature of the materials in each class and are noted as Groups A, B, C, D, E, F, and G. This is a descending order, with group A denoting acetylene gas which has the highest explosion potential, Group B representing compounds such as Hydrogen, and groups C and D denoting the most commonly encountered compounds such as gasoline and propane. Groups E, F and G denote combustible dusts and are based on the properties of specific types of materials that make up these dusts according to their conductivity and flammability. Metallic dusts are high conductive and so receive a Group E rating. Group F contains highly flammable dusts such as Coal and Carbons, and Group G contains more common materials such as Flour, Starch, Sugar and the like.

Explosion proof equipment thus must meet the requirements of a hazardous location based on how that environment is classed. A Class 1 Division 1 Groups A, B, C and D fixture will thus be of the highest protection rating and suitable for a variety of conditions and materials, Class 1 Division 2 fixtures will be suitable for combustible dusts with occasional exposure, and so on as classes and divisions vary.

Of the utmost importance for those operating or managing hazardous locations is ensuring the suitability and compliance of explosion proof or intrinsically safe equipment. As can be seen from the aforementioned ratings system, simply because equipment is approved for hazardous locations, does not impart suitability for all locations. Equipment must be matched to the hazardous location in order for operators to be in compliance with regulations or else safety is compromised and citations are possible.  

To ensure compliance, it is important to ensure that equipment carries the proper certification in the form of tags affixed to the fixture and the proper accompanying literature if necessary. Some manufacturers produce inferior products or misleading labeling, such as is the case with fixtures that are labeled “vapor proof”, but do not carry a statement making explicit their non conformance to explosion proof standards. Operators should only select equipment that carries clear certification and attempt to avoid the temptation to base judgments entirely on price, and instead deal only with reputable and established manufacturers and suppliers. The critical nature of hazardous locations and the high risk for workers within these locations makes ensuring compliance and safety mandatory, with little room for justifying compromise.

The history of the industrial workplace is littered with examples of disaster and tragedy that resulted from attempts to cut corners and poor adherence to hazardous location safety compliance. The loss of life, damages to operations, and oftentimes extreme penalties, make ensuring compliance more cost effective than any possible cost cutting be it either through failure to provide training or use of improper or poor quality equipment. By ensuring compliance, operators are ensuring not only the safety of their employees and the workplace, the continued long term production of their operations.