NFPA 921 advises the use of a systematic approach to fire investigation that is best embodied by the scientific method. The scientific method includes the steps of collecting data, analyzing that data, developing a hypothesis, and then testing that hypothesis. The final step of this process, testing the hypothesis, can be done either physically or analytically. In some cases, a physical test may be conducted to confirm or falsify some aspect of the hypothesis. However, in many cases creating a physical test may be difficult or even practically impossible. It is these cases, and others, where analytic testing using computer simulations may be helpful to the fire investigator.