Flue Gas Measurement basics There is a lot to understand when testing the combustion of gas appliances. This is just a quick overview for those who haven’t done it, it’s not meant to be a tutorial for the process or equipment and tools. Basically with this boiler I can verify proper venting, gas pressure and performance. This combustion test is simply being performed to verify proper performance. The boiler combustion chassis/controls has more input on performance than we do because of how it is