Residential Building Inspector B1Public Safety and Special ConstructionMedium
An inspector is reviewing the clearances for a Type B gas vent. What is the minimum required clearance from the vent to combustible materials?
- A6 inches
- B0 inches
- C2 inches
- D1 inch
Show answer & explanationAnswer & explanation
Correct answer: D. 1 inch
IRC G2427.6.5 (503.6.5) specifies that Type B gas vents shall be installed with not less than 1-inch clearance to combustible materials. This is a standard clearance for these specific vents.
Why the other options are wrong
- A. This clearance is excessive for Type B vents and typically applies to single-wall metal chimneys or connectors.
- B. Zero clearance is typically for specific appliance connectors or factory-built components, not Type B vents.
- C. This clearance is often for masonry chimneys or some other vent types, but not Type B.
Type B Gas Vent Clearance
Type B gas vents are double-wall metal pipes designed for venting gas appliances. They have a specific minimum clearance requirement to combustible materials to prevent fire hazards.
- Used for Category I gas appliances.
- Double-wall construction.
- Minimum 1 inch clearance to combustibles.
Memory trick: B-vents need just one inch of space, to keep combustibles in their proper place.