Which vent type is installed when the chart number doesn’t work?

• A. Direct vent
• B. Chimney vent
• C. B vent
• D. PVC vent

Answer: (C)

When a venting chart doesn’t provide a matching entry for a appliance setup, the standard approach is to use a B-vent. B-vent is designed for gas appliances that vent through a chimney using natural draft—the hot exhaust gases rise up the vent and out through a masonry or factory-built chimney. It’s typically a double-wall metal vent rated for the temperatures involved and is installed vertically to create the necessary draft.

This contrasts with other vent types: direct vent brings in outdoor air and vents exhaust separately, and PVC venting is used for high-efficiency sealed-combustion appliances that exhaust through plastic pipe. A chimney vent term can be more general, but when the chart number can’t be applied, B-vent is the conventional choice for appliances venting into a chimney via natural draft.