On March 23, 2005, a vapor cloud explosion at a Texas City oil refinery injured more than 180 people and claimed 15 lives. The deaths were a result of a blast pressure wave striking contractor trailers located near the explosion fuel source. Accident investigation determined the trailers were sited inappropriately close to relief device outlets which contributed heavily to the loss of lives. As a result, API Recommended Practice (RP) 753 [API RP 753, Management of Hazards Associated with Location of Process Plant Portable Buildings, First Edition, American Petroleum Institute, Washington, DC, 2007] was drafted in 2007. API RP 753 provides guidance to reduce the risk of injury as a result of fire, explosion, or toxic release for inhabitants of portable buildings located in the proximity of refineries, petrochemical and chemical operations, natural gas liquids, extraction plants, and other industries. This article outlines a conceptual methodology to evaluate blast resistant modules for use in potentially hazardous locations. (c) 2014 American Institute of Chemical Engineers Process Saf Prog 34: 137-140, 2015