chamber, is not known, smoke readings, CO, and flue gas temperature should be taken to determine if the draft setting is correct on oil equipment. CO, readings and a check to see that no CO is present are essential on gas fired equipment. Gas — The usual practice with commercial and industrial gas fired plants is to adjust for CO, readings between 9% and 10%, or even higher, but this will depend upon the analysis of the gas and the type of burner equipment. Consult with the burner manufacturer.