There are multiple ways to approach the COOLmix transition. First, the burner control system can have a ramping function that brings in and takes out COOLmix gradually until it meets the set point. Second, the AIRmix zone can be designed to fire high enough to achieve AIT, and then the COOLmix is introduced gradually while AIRmix heat release is reduced. Third, if the customer furnace is expected to be near the AIT temperature, the burner can be supplied with a second set of COOLmix tips that can operate below AIT. This allows for a smooth transition between the COOLmix zones as the AIT is crossed. We have incorporated a dead band to avoid oscillating if this function is chosen.