System 636 PVC is classified as Type BH Class IIA vent, suitable for use on appliances with flue gas temperatures up to and including 65ºC (149ºF). Colored white with unique blue certification markings, System 636 PVC pipe is made to sturdy Sch. 40 dimensions to provide a strong, rigid pipe for the application. A full range of System 636 PVC vent fittings and accessories are also offered.