This paper is based on findings resulting from ASHRAE Research Project RP-1517.Combustion oscillations commonly occur in boilers, furnaces, and water heaters. At the present time, there is no systematic process for diagnosing the probable cause of an instability and solving the problem. Moreover, few design guidelines have been presented in the literature for avoiding thermo-acoustic instabilities before they occur. The current paper details steps that can be taken to prevent and diagnose combustion instabilities from the early stages of the designprocess through production.