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A new metallic foam known commercially as 'Retimet' was examined for the purpose of protecting industrial equipment for use in flammable atmospheres. The metal foam functioned as a flame arrester when mounted on the casing of such equipment and relieved pressure resulting from ignition of flammable gas within the equipment but prevented the emergence of flames to the outer atmosphere. Cubical enclosures up to 28 litres (1 ft^3) in volume have been tested with propane/air and ethylene/air mixtures using two different porosity grades of the metal foam. The pressure developed inside the enclosure was found to be dependent upon the vent area and the porosity of the metal foam. A limiting vent area was found below which damage to the arrester would occur and the outer atmosphere would be ignited. The mechanism of the explosion transmission through the arrester was established.