Gas and chimney venting products connect to the exhaust of a combustion system and provide a path to remove them from the building. They are built using heat-resistant materials and seals that keep exhaust gases contained in the exhaust duct. Gas vent pipes and fittings are the primary components of an exhaust gas duct run. They fit together and create sealed paths for exhaust gases to escape the building. Chimney liners, kits, and fittings install into existing chimneys and provide a heat-resistant path for exhaust gases to escape. Penetrations and supports for gas venting provide pathways for exhaust vents to travel through the building's shell and secure it into place.