Description / Abstract: This document provides guidance for the use of various Secondary Barrier Systems as acceptable means of compliance with current U.S. regulations, as well as an evaluation of best practices, and other considerations to be taken into account when determining compliance with these regulations. The guidance recommended is one means of ensuring that the equipment will perform its intended function satisfactorily under all conditions normally encountered in routine operations. Any regulatory application of these standards is the sole responsibility of the appropriate governmental agencies.