Hey, I would really appreciate some feedback on this method of evaluating combustion air.
Unnecessary Holes in the Building
Contractors often cut combustion-air holes in ceilings, floors, walls, and doors without knowing whether the combustion appliance zone (CAZ) needs additional air. These new openings can lead to unintended consequences like pressurizing or depressurizing the CAZ or admitting cold drafts.
Combustion Air Evaluation
The best way to evaluate the combustion air is with an electronic combustion analysis of the building’s combustion appliances. During worst-case testing, the combustion analyzer measures both CO and oxygen (O2). The O2 is an indicator of excess combustion air.
- Sample undiluted flue gases as they leave the appliance’s heat exchanger during worst-case conditions.
- If the reading from the combustion analyzer is more than 5% with minimal CO, this indicates that an adequate amount of combustion air is available.
- If the O2 reading from the combustion analyzer is between 0% and 5%, this indicates that combustion air is inadequate. We would expect significant CO with this O2 reading
At 5% or more of flue-gas oxygen, additional indoor or outdoor combustion air is usually unnecessary. If the O2 is between 0% and 5%, open a nearby window or door a little. If the O2 level rises to an acceptable level, install a combustion air supply from one of these areas.
- Another indoor space
- A ventilated intermediate zone, such as a ventilated attic or ventilated crawl space.