This API Standard specifies the requirements for comparative testing of block valve stem packing for process applications where fugitive emissions are a consideration. Packing(s) shall be suitable for use at -20°F to 1000°F (-29°C to 538°C). Factors affecting fugitive emissions performance that are considered by this Standard include temperature, pressure, thermal cycling, mechanical cycling and corrosion.This standard does not provide acceptance criteria for valve packing, nor is it intended to replace proof testing of valve assemblies or valve production testing. This standard establishes requirements and parameters for fugitive emissions, corrosion, and packing material packing tests. The test methods apply to valve packing for use with the rising and rotating stem motion.