Which of the following is NOT a mathematical model used in fire investigation?

The identification of "Redundant analysis" as not being a mathematical model used in fire investigation is based on an understanding of the functions and applications of the other options.

Heat transfer models are essential in fire investigation as they help in understanding how heat spreads through materials and environments during a fire event. This is crucial for determining fire behaviors and potential damage to structures and materials involved.

Flammable gas concentration models are also relevant, as they provide information about the potential for ignition and combustion dynamics of gases present during a fire. Investigators use these models to assess risk factors and the likelihood of fires starting due to the accumulation of flammable gases.

Structural analysis plays a vital role in evaluating how fire affects building integrity, and it applies mathematical principles to determine the structural response to heat and fire loadings. This analysis is crucial for understanding the collapse of structures during fires.

In contrast, redundant analysis does not specifically relate to fire investigation methodologies or mathematical modeling. Instead, it typically refers to a process or technique used in various fields to enhance reliability by duplicating components or systems. Thus, it does not fit within the context of mathematically modeling phenomena or behaviors associated with fire investigation.