This paper describes the results of extensive research to determine the limit of safety against flame transmission for sintered metal flame arrester elements when stressed by a flashback in a fuel-gas/oxygen mixture and when stressed through a stabilized burning of a flowing mixture of fuel-gas and air and of fuel-gas and oxygen at the sintered metal element. On the basis of the results of these investigations, the limit of safety against flame transmission for sintered metal flame arrester elements can be estimated and the conditions for testing can be specified. An analysis of the protection of gas outlets on gas distribution lines for welding, cutting and allied processes has been carried out, resulting in recommendations for necessary changes to the regulations for testing of safety devices with sintered metal flame arrester elements, which should be made in the next revision of the corresponding technical regulations for acetylene installations and calcium carbide stores (TRAC), and the standards DIN 8521, EN 730 and ISO 5175.