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Inspecting Unvented Gas Appliances

Home inspectors see unvented gas appliances used for a supplementary heat source or in a fireplace as ventless logs. There are also many freestanding units. These units do not require ventilation to the outside and are made to not produce large amounts of harmful gasses. Many of these units have oxygen sensors that will shut down the unit if the oxygen is depleted. These units have created much controversy among home inspectors and indoor air quality experts. As houses get “tighter” and air exchanges are much less with new building standards, some experts do not recommend they are used. Unvented appliances also create moisture. There have been some fires associated with these units. They are not supposed to be used as an only or primary heat source. The fuel source could be natural gas or propane. Some units also have a blower. Most units are not recommended for use in bedrooms and bathrooms unless the size of these rooms are adequate based on the manufacture’s recommendation. Home inspectors should never light the pilot. The unit can be started using normal operating controls. The inspector is limited to report if the unit responded at the time of inspection. Many home inspectors have an opinion of unvented gas appliances. Here is what a home inspector should be looking for:

  • Ducts supplying other areas should not be connected to other rooms
  • It is recommended that only one ventless unit is installed in the house
  • They should not be installed in mobile homes, trailers, or recreational vehicles
  • A sediment trap or drip leg should be installed on the gas line
  • A dedicated shut off valve should be installed and in close proximity to the unit
  • If installed in a garage or basement it should be at least 24 inches above the ground
  • Many manufacturers recommend providing additional fresh air or combustion air by opening a window in the room when the appliance is operating
  • A Carbon Monoxide detector should be installed in the room where the appliance is located
  • Clearance to combustibles may vary depending on the manufacture, however 36” is a good rule of thumb for a visual home inspection
  • Black soot noted in or around the unit would indicate the unit is not operating properly
  • The flame on any gas or propane appliance should be blue
  • Any gas odor would be a major defect

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