The factors leading to resonant combustion in tunnel burners have been investigated and the results have indicated the importance of the upstream mixture feed length. It has been established that the combination of the flame and the tunnel tends to generate organ pipe oscillations at a frequency which depends, among other parameters, on the tunnel length. These oscillations are propagated upstream into the unburned mixture and, in the presence of some type of acoustic termination, there is the possibility of standing waves being set up in the mixture feed system. The standing waves cause pulsations in the mixture flow, giving rise to fluctuating component of heat release and if they are in phase with the natural tunnel oscillations, resonance will occur accompanied by “screaming” combustion. In industrial air blast burners there is no precise upstream acoustic termination but the venturi injector or air nozzle has been found to act as a rather indefinite “open” end. In general, however, practical burners showed a marked similarity to the idealized experimental type. The tunnel length and mixture feed arrangement exert a considerable effect on the degree of resonance and a method has been suggested for the suitable matching of these two components in order to avoid oscillations. Recommendations have also been made for the positioning of bends in the mixture manifold.