If you are working in the building science, weatherization or HVAC industry, combustion analyzers, personal CO protection, a draft gauge, and smoke pencil are required for your and your clients safety and to determine the safe operation of combustion appliances. While you may not be qualified to correct the combustion problems you may find or create, you must at minimum need to know if they exist. If you are not qualified, licensed or trained to make repairs to a heating system consult a qualified and trained HVAC contractor preferably who has been formally trained with dealing with issues of Carbon Monoxide (CO) and combustion testing. TruTech Tools offers free combustion testing classes.
When it comes to combustion analysis, we wrote the manual. No kidding, we really did! Down load it here for free. TruTech Tools Combustion Guide