This presentation covers venting requirements for high efficiency hydronic heating systems, including venting basics as well as special gas venting systems for Category II, III & IV. Appliance manufacturer’s requirements and proper system design will be discussed along with Code Compliance with National Fuel Gas Code and design Criteria for NFGC Compliance. Proper system design is examined with pressure drop and draft calculations as well as the results of inadequate draft and over draft control. Finally, proper application of design is reviewed as it pertains to high efficiency, condensing hydronic heating systems.