This section deals with the setup of combustion cases for HVAC simulations, where it is important to accurately model the combustion process. Such processes are known as "combusting fire" simulations, as opposed to "inert fire" simulations.

Using a combusting fire simulation is the most accurate way to model fires in all HVAC cases. It is particularly important in cases when the fire is under-ventilated, or when the ventilation cannot be easily predicted. The drawback is the additional computational expense involved in solving a full combustion model as part of the main solution.