## 3 Results and Discussion  
The results of the air jet velocity profiles measured on the surface of the outlet hole are shown in Figure 2 for fan 1 and Figure 3 for fan 2. Due to the considerable amount of measurement data, information related to measurement accuracy has not been marked on the trifunctional charts. This information is included as an Appendix A (Tables A1 and A2), in which the results of the average velocities, for each measurement point, are shown separately for each opening area of the FRC flow damper (P1-P5). In Tables A3 and A4, a summary of the average pressures recorded on each floor (I-IV) for all five throttle opening surfaces (P1-P5) is presented. On the other hand, Table A5 shows the volumetric flow rate that was pumped through the object, for five areas of the measurement plane opening, for both fan units. Analyzing the characteristics of air flow velocity in the outlet (Figures 2 and 3), it can be observed that as the size of the outlet increases, the highest flow velocity is concentrated in the lower and upper parts of the outlet. The flow velocity values coincide with the results of [PERSON] et al. in 2018, who reported average flow velocities in the outlets ranging from 2 m/s to 7.6 m/s ([PERSON] et al., 2018). The highest flow velocity was obtained for a hole with a shape similar to that of a full bore outlet ([PERSON] et al., 2018). Additionally, studies by [PERSON] et al. in 2018 and [PERSON] in 2013 characterized flow velocities in the outlet in similar ranges, from 1 m/s to 3 m/s ([PERSON] et al., 2018; [PERSON] and [PERSON], 2013). Figure 1: Configuration of the test system: 1—the fan, 2—the window opening (measuring plane with the division of rest of the measuring points, (from the left) P1–24, P2–48, P3–72, P4–96 and P5–120), 3—the measuring probe (TSI thermo anemometer), 4—the body of the test stand and the shutter modifying the size of the outlet opening, and 5—the guides for transporting the measuring probe. The effect of the size of the outlet cross-section on the flow parameters--volumetric flow rate and static pressure value--is shown in Figure 4. The presented flow characteristics were made on the basis of the data in Tables A1-A5. Analyzing the obtained results of the flow parameters (volumetric flow rate as a function of pressure), it is indicated that both fans obtained the highest values of volumetric flow rate, for the largest area of the outlet opening--P5 (1.2 m\({}^{2}\)). Under these conditions, fan 1 pumped 14,020.92 \(\pm\) 702.19 m\({}^{3}\)/h, while fan 2 pumped 15,656.33 \(\pm\) 838.66 m\({}^{3}\)/h. The smallest volumetric flow rate was recorded for the smallest measurement plane opening area (P1--0.24 m\({}^{2}\)), where fan 1 pumped 4624.17 \(\pm\) 116.70 m\({}^{3}\)/h and fan 2 pumped 4884.66 \(\pm\) 190.20 m\({}^{3}\)/h. Analyzing the pressure parameter, it should be pointed out that the largest values were obtained for the smallest opening areas of the P1 damper (0.24 m\({}^{2}\)). Fan 1 generated pressures of 39.7 Pa, while fan 2 generated pressures of 27.9 Pa. A limitation of the inference from the conducted analyses is the influence of the temperature inside the building during rescue fire operations [24, 25, 26]. Figure 3: Airflow velocity in the outlet for fan 2, set at a distance of 5 m from the door opening, with an angle of inclination of 6\({}^{\circ}\) and an area of the outlet opening of at (**a**) P1, (**b**) P2, (**c**) P3, (**d**) P4, and (**e**) P5. Figure 2: Airflow velocity in the outlet opening for fan 1, positioned at a distance of 1 m from the door opening, with an angle of inclination of 17\({}^{\circ}\) and an area of the outlet opening at (**a**) P1, (**b**) P2, (**c**) P3, (**d**) P4, and (**e**) P5. As presented in Figure 4, both cases differed substantially in terms of their characteristics (which are generated in the building pressure in relation to the flow rate). The differences were highest in low restrictor areas when the ventilator jet encountered the highest backpressures.