An alternative methodology to that of United Nations, Appendix 5, Sample Method, has been developed by the Organic Peroxides Producers Safety Division of the Society of the Plastic Industry (OPPSD/SPI) to assure the safe emergency venting of organic peroxides in an approved container. The methodology is applicable for designing a new container for an existing or new organic peroxide. Bench-scale testing with a 10 liter vessel determined the maximum pressure (spike) generated during a thermal decomposition/overpressurization vs. the ultimate, structural strength of the container measured and/or calculated. The methodology has been tested full scale with a United Nations 6(c)fuel fire. Container deformation, so long as there is no fragmentation, is permitted with the proviso that the container be retired from service following an incident. The methodology as developed, reflects advances in technology while "harmonizing" to a maximum extent with the United Nations, Appendix 5, Sample Method.