Adding or Removing Liquid and Solid-Fuel Appliances From Chimneys and Vents

Description of Potential Problems when Adding or Removing Fuel-Burning Appliances
Every fuel-burning appliance has diff erent characteristics that will aff ect the operation of a chimney or vent. Adding or removing appliances may cause a chimney or vent that once operated properly to operate improperly. Problems that may occur include backdrafting of exhaust gasses into the home and condensation of moisture that can quickly damage the chimney or vent. Backdrafting and damaged chimneys and vents are a signifi cant safety hazard.

Recalculate Size of Chimneys and Vents when Adding or Removing Appliances
1. Recalculate the size of a chimney or vent when adding or removing a fuel-burning appliance. The new chimney or vent size could increase, decrease, or remain the same depending on the type and efficiency of the appliance added or removed. Account for the new size requirements based on all fuel-burning appliances att ached to the chimney or vent. To calculate the required size of a masonry chimney used to vent an oil-burning appliance, use NFPA 31. To calculate the required size of a gas appliance vent, use IRC Chapter 24.

Cleaning and Inspection of Chimneys and Vents when Adding or Removing Appliances
1. Inspect chimneys and vents when adding or removing fuel-burning appliances. Ensure that the flue is continuous and free of cracks, damage, or deterioration that could allow escape of combustion products. Ensure required clearances to combustible materials and ensure that required firestops and fireblocks are installed.
2. Clean flues that have been used for solid or liquid-fueled appliances before inspecting the flue.

Chimney Cleanouts
1. Install a cleanout opening with a tight-fitting, noncombustible door and with an opening height of at least (≥) 6 inches and located at least (≥) 6 inches below the lowest chimney inlet opening.