There has been a history of failures involving pressure relief devices used on cylinders in NGV service. Recent incidences in North America involving the premature release of gas from certain devices brought into question the validity of existing standards (S-1.1) used for NGV pressure relief devices. The pressure relief devices defined in the standard were not specifically designed to address NGV service conditions. Accordingly, the NGV industry recognized that changes to the standard were required to accommodate newer technology devices and to more closely reflect NGV service conditions. An NGV industry task group was subsequently formed to develop a new pressure relief device standard, ANSI/AGA PRD-1, 'Basic Requirements for Pressure Relief Devices for Natural Gas Vehicle (NGV) Fuel Containers'. Powertech Labs Inc. has recently completed work to establish the validity of the proposed ANSI/AGA PRD-1 standard in a program funded jointly by Gas Technology Canada, the Gas Research Institute (Chicago) and British Gas. The PRD-1 performance tests were applied to a wide range of existing and prototype pressure relief device designs manufactured in North America and Europe to validate the proposed standard. The performance tests were found to be successful in replicating the in-service performance of pressure relief devices. Four of the tests (thermal cycling, salt corrosion resistance, stress corrosion cracking resistance and vibration) required certain procedural revisions to be satisfactory. Specific recommended changes to these procedures were forwarded to the appropriate ANSI/AGA committee for consideration. Implementation of Powertech's findings regarding the proposed PRD-1 standard will significantly increase the long term reliability of pressure relief devices used in NGV service. The identification of test requirements for these components will promote the development of reliable (safer) devices of lower cost. In addition, the performance tests could be used to reduce the number of full-scale bonfire tests required on cylinder designs.