In order to understand how to maintain certification compliance of equipment used in hazardous (classified) locations, one must first have an understanding of what a hazardous (classified) location is and what the requirements are for the equipment certification. These will be explained in Part I by Cheryl Gagliardi, a senior engineer with FM Approvals. Part II will cover recommendations for end-user actions for maintaining the certification compliance and will be provided by Bob Baker, an industry consultant to Emerson Process Management. (C) 2008 Elsevier B.V. All rights reserved.