Expanded metal mesh and polymer foams of appropriate pore or cell size and sufficient surface area per unit volume can suppress deflagrations of gas/vapor-air mixtures. This paper reviews the requirements that have been established for use of these materials in military aircraft fuel tanks. Extensions and generalizations of these requirements for other applications have been developed and incorporated into the 2008 edition of the NFPA 69 Standard for Explosion Prevention. The new NFPA 69 requirements for testing, evaluating, and installing these materials are summarized here along with an explanation of the basis and rationale for these requirements. (C) 2007 Elsevier Ltd. All rights reserved.