Approaches Other Than Explosion-Proofing to Electrical Safety

Instrumentation, control, and electrical installations in hazardous areas are usually governed by the rules of Article 500 of the National Electrical Code (NEC). Further guidance is found in the Recommended Practices of both the American Petroleum Institute and the Instrument Society of America, as well as publications of other organizations such as the National Fire Protection Association. It is the intent of this paper to show some of the methods, other than explosion proofing, available to meet the requirements of the NEC. These include intrinsic safety, purging and pressurization, physical isolation, etc. An attempt will be made to discuss the advantages and disadvantages of each method. The methods discussed are those that have secured reasonable acceptance by users in the U.S. Some items of the bibliography show others used in certain other areas that may be of some interest. Also included is a discussion of what to do when substances not presently listed in the NEC are encountered. A bibliography is supplied to allow the reader to find detailed data for further study.