## 3 Results and Discussion  
The result of volumetric flow rate depending on the positioning distance of the positive pressure ventilator (calculated based on the method described by [PERSON] et al. in  
Figure 3: Visualization of the numerical model created for the simulation test to evaluate the characteristics of the airflow velocity profile on the surface of the door opening, where 1—positive pressure ventilator; 2—detector of airstream velocity; 3—mock-up simulating the door opening. 2023) [27] is presented in Figure 4 and in Appendix A in Table A9. The visualization of the airflow generated by the ventilator in the CFD simulation is shown in Figure 5.  
The results of the volumetric flow rate measurements taken in the immediate area of the ventilator's impeller are presented in Appendix A in Table A1. The results of the velocity profile of the airflow measured on the surface of the mock-up of the door opening during experimental tests and CFD simulations are shown in Figures 6-10. Due to the way the velocity profile results are presented in the figures, information on measurement accuracy is not indicated. These details are provided in Appendix A in Tables A2-A8, which include the average values of the airflow velocity and measurement errors on the surface of the door opening. The visualizations of the obtained results of the airflow velocity profile generated by the ventilator (Figures 6-10) are presented. Larger differences are observed at closer positions of the ventilator, where large velocity gradients are observed at the door opening. As a result, the analysis with a fixed spatial resolution directly resolves a smaller part of the turbulent scales. In the case of larger distances between the ventilator and the door opening, where the shear layer is much thicker, this also leads to larger dominant vortical structures--the differences between CFD and experimental results are negligible. Importantly, the application of the boundary condition on the ventilator based on the measured velocity profile allows for high convergence of the volumetric flow rate in the mock-up of the door opening, regardless of the ventilator's distance. In all of the investigated configurations (including the experiment, simulation, and various ventilator positioning distances), the airflow was concentrated in the lower area of the door opening (up to a height of 900 mm). Referring to the obtained volumetric flow rate values, it is indicated that the ventilator during the experimental tests generated the highest flow rate when positioned at a distance of 7 m (30.156 m\({}^{3}\)/h), while in the CFD simulation, the highest flow rate was at a distance of 6 m (29.397 m\({}^{3}\)/h). The lowest flow rate was obtained at a distance of 1 m. During the experiment, the ventilator pumped a flow of 20.123 m\({}^{3}\)/h, while during the simulation, it was 19.743 m\({}^{3}\)/h. [PERSON] and [PERSON] conducted similar tests for ventilators that generated flow rates of 30.800 m\({}^{3}\)/h for gasoline engine-powered ventilators and 30.000 m\({}^{3}\)/h for electrically powered ventilators [39]. The results of studies conducted by [PERSON] et al. Figure 4: The characteristic of the volumetric flow rate of a positive pressure ventilator obtained during experimental tests in real conditions and CFD simulations at a test setup for evaluating the velocity profile of the airflow at the door opening surface. in 2023 showed that the tested ventilators generated a volumetric flow rate ranging from 14.021 m\({}^{3}\)/h to 15.656 m\({}^{3}\)/h, depending on the type of ventilator [40]. In comparative considerations (between experimental studies and CFD analysis), the flow rate stream showed a level of convergence described by a percentage difference ranging from 1.6% (at a positioning distance of 4 m) to 3.8% (at 7 m). In 2003, [PERSON] and [PERSON] were the first to present a method for assessing velocity profile parameters in free flow for positive pressure ventilators and conducted CFD simulations in free flow [21].