## 2 Materials and Methods
### Fire Models Selected for the Case Study  
It is essential to select the appropriate fire model for each task. The choice of the model is closely related to the following areas:  
* the objectives of the solution (evaluation);
* the extent and quality of the input data;
* the extent and quality of the required output data;
* visualisation quality requirements;
* the characteristics of the model and its potential to address the stated objectives. The Model of Fire and Smoke Transport (CFAST) and the Fire Dynamics Simulator (FDS) were chosen for further evaluation. The CFAST and FDS models enable to perform simulations when entering different sources of fire. In this case, the so-called t-square fire was used, which is characterized by different fire dynamics for various groups of production and operations. However, this is only one option. As was previously mentioned, the used fire models allow to perform simulations for different fire sources. In general, it is possible to use more centers of fires, not just only one. It can be stated that only the fire model FDS enables to distinguish the different sources of fire, for which it also allows to perform a parallel calculation, i.e., it enables to apply more than one processor in the calculation process. Of course, each of the fire models has its own specific advantages and disadvantages. The type of the solved task, the scope and quality of the input data, and the required scope and quality of the input data are the decisive aspects necessary for a proper choice of the suitable fire model. The fact whether the model is currently being developed and verified on a long-term basis is absolutely substantial. When evaluating the performance of the fire models (this affects the choice of the model itself), it is also necessary to take into account the basic attributes on which the model is based, i.e., what kinds of the sub-models are used in order to solve the sub-processes and what are the limits of the model. In their response, the authors presented only the basic aspects related to the choice of a suitable model and to assessment of its performance. The turbulence was simulated using the Large Eddy Simulation (LES) method. The \"most used\" mathematical CFD fire model--the FDS program--is based on this approach. CFAST is a two-zone fire model used to calculate the evolving distribution of smoke, fire gases and temperature throughout compartments of a building during a fire. These can range from very small containment vessels, on the order of 1 m\({}^{3}\) to large spaces on the order of 1000 m\({}^{3}\)[22; 23]. The modeling equations used in CFAST take the mathematical form of an initial value problem for a system of ordinary differential equations (ODEs). These equations are derived using the conservation of mass, the conservation of energy (equivalently the first law of thermodynamics), the ideal gas law and relations for density and internal energy. These equations predict as functions of time quantities such as pressure, layer height and temperatures given the accumulation of mass and enthalpy in the two layers. The CFAST model then consists of a set of ODEs to compute the environment in each compartment and a collection of algorithms to compute the mass and enthalpy source terms required by the ODEs [22; 23; 24]. Fire models based on Computational Fluid Dynamics [24] are widely used for the assessment of fire development. One of the most promising models based on this foundation is the FDS model. The model was developed at the National Institute of Standards and Technology in the USA [25] in collaboration with the Technical Research Centre of Finland in Finland [13]. The FDS model has been validated during its development and is also now being further developed. To facilitate the work, it is possible to use the graphical interfaces PyroSim [14] or Blender FDS [15]. FDS solves numerically the Navier-Stokes equations for temperature-controlled flow, with emphasis on heat and smoke transfer from the fire.