Water Heater venting - part I: Know your water heater, know your venting options

摘要

In the early 1990s, the gas industry decided to redefine venting requirements of gas-fired appliances. One of the first steps was to develop new categories for classifying the venting of gas-fired appliances. The categories were simply Category I, II, III and IV. A Category I is your standard, atmospheric-venting, gas-burning appliance. Most water heaters fall into the classification of a Category I appliance. Category II appliances are atmospheric-venting; however, the products of combustion may condense in the vent system.