IAAI Certified Fire Investigator (CFI) Practice Test 2026 – All-in-One Guide to Master Your Certification!

Heat of combustion is the total energy released when a fuel burns completely with oxygen to form stable products (usually CO2 and H2O). It’s treated as a property of the fuel, effectively a constant per unit mass or per mole under defined conditions. This value is what fire investigators use to estimate the energy potential of a fuel and predict fire behavior. In practice, it’s commonly expressed as higher heating value (HHV) or lower heating value (LHV), depending on whether the energy in the water vapor is included.

Other terms describe different things: heat of ignition is the energy required to start combustion, not the energy released; heat release rate is how quickly that energy is liberated over time during a fire; heat flux is the rate of heat transfer per unit area.