The investigation of a gas-related fire or explosion typically involves testing the integrity of the gas system. Oftentimes this testing reveals one or more leaks of various sizes. The investigator must then evaluate the cause of each leak and/or its potential in contributing to the cause of the incident. Two methods commonly used to evaluate the potential causal role of a leak are full scale testing and mathematical modeling. Although full scale testing is preferred, it may be cost prohibitive and impractical. In these cases, the alternative is mathematical modeling. The question that arises with the use of a mathematical model, however, is how accurately it predicts the gas concentrations that were actually present during the incident under investigation.