Lots of energy auditors, inspectors, HVAC folks, and air sealers are confused about how, when, and why it is important to test combustion appliances. They often don't know what the test is supposed to tell them... and once they get an answer from their equipment, they don't necessarily know what to do with the answer. They wonder "Is this a good number? Or a bad number? Does it pass or fail? Can I keep working or do I have to stop? Do I have to undo something I just did or fix a new problem?" It is scary out there once you start testing and understand the test results. A large percentage of the homes we visit have gas leaks. Many water heaters and heaters have inadequate draft pressure and they backdraft. Many have high CO levels in the flue gasses.
I was confused. But not anymore! What a relief. Now, it's easy for me to explain the whys, hows, whens, and whats to others so they can get it too. Be patient with yourself as you learn - but be on the safe side and have another person test in and test out while you learn.
The current issue of Home Energy Magazine includes an article I wrote about combustion testing. Maybe it will help you.
If you have been certified as a BPI Building Analyst to do combustion safety and gas leak testing and you don't do it during an energy assessment, you need to notify the occupant every time that they should have that testing done by a qualified technician. Whether they ask about it or not. I can't imagine that too many homeowners know to ask such questions. How can you do a blower door test on a house or recommend air sealing without analyzing the combustion safety ramifications? Being certified raises us to a higher level of expectations from our clients. I have seen too many houses that have had problems when only the air sealing/blower door analysis has been done and pursued. Utilities/HVAC contractors don't do comprehensive gas leak testing. Fixing gas leaks saves energy and can save lives.