## 2 Materials and Methods  
The tests were performed on commonly used mobile fans, a conventional fan and a turbo fan. Detailed parameters of the positive pressure ventilators used are presented in Table 1.  
The flow tests were carried out in a 7-story building, inside which 4 storys (constituting a gas exchange line) were adapted for testing by sealing the remaining storys. Only 4 floors \begin{table}
\begin{tabular}{l l} \hline \hline
**Positive pressure ventilator 1** & \\ \hline Combustion engine & Briggs and Stratton 750 \\ Maximum volumetric flow rate (declared) & 30,000 m\({}^{3}\)/h \\ Maximum power of the engine (at rotational speed 3600 rpm) & 4.4 kW \\ Displacement capacity & 163 cm\({}^{3}\) \\ \hline
**Positive pressure ventilator 2** & \\ \hline Combustion engine & Honda GX 200 \\ Maximum volumetric flow rate (declared) & 31,799 m\({}^{3}\)/h \\ Maximum power of the engine (at rotational speed 3600 rpm) & 4.1 kW \\ Displacement capacity & 196 cm\({}^{3}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characteristics of mobile rescue fans. were selected for the tests, in order to maintain a compromise between the measuring range of the generated volume flow rates and at the same time maintaining the configuration reflecting the staircase of a multistory building. The tested cubic capacity (for 4 storys) was 198 m\({}^{3}\), respectively. On the fourth story, in a window located on the southeast wall, a FRC test stand for evaluating velocity profiles had been installed, which is the equipment of Scientific and Research Centre for Fire Protection--National Research Institute, Jozefow, Poland [8]. The test stand consisted of the following elements:  
* A steel body allowing for a tight fit to the window opening;
* A special screen wound on a roll made of plastic (intended to change the size of the outlet opening) mounted on steel guides;
* A measuring module on which a thermoresistance anemometer was mounted, which moved in a synchronized way on the surface of the measuring plane (communication with the controller was carried out using a radio module);
* Guides made of aluminum profiles dedicated to the transport of the measuring module;
* A drive (stepper motor), allowing the measurement module to be moved. The test stand had the ability to evaluate the flow velocity field taking into account the variable size of the outlet opening area, but these tests were performed for the full throttle opening area (1.2 m\({}^{2}\)). The test configuration of the stand is shown in Figures 1 and 2. During the course of the tests, measurements were made:  
* Distribution of air flow velocity profiles on the surface of the outlet opening. The measurement was performed at 120 points located evenly on the surface of the FRC measurement plane. The measurement module was equipped with a TSI 8455 thermoressive anemometer (with a measurement range of 0.127-50 m/s and an accuracy of 1%) (m/s). * Pressure values (using Setra pressure transducers) distributed 1 piece on each of the 4 floors with a measurement range of 0-100 Pa and accuracy of 0.25%. Figure 1: Configuration of the test system, where: 1—fan, 2—window opening (measuring plane with 120 points division), 3—measuring probe (TSI thermo anemometer), 4—test stand body and roller shutter modifying the size of the outlet opening, 5—guides for transporting the measuring probe. The acquisition frequency of the flow velocity and pressure parameters was 10 Hz, and the measurement duration corresponded to a value of 30 s. During the tests, the volumetric flow rate was evaluated for varying fan positioning distances from 1 to 7 m. For each test, the rotor angle was set so that the rotor axis was directed as close as possible to the center of the doorway. For fan 1, the angle of inclination was 1, 2, 3 m--17\({}^{\circ}\); 4 m--11\({}^{\circ}\) and 5, 6, 7 m--6\({}^{\circ}\), respectively. Fan 2 was positioned as follows 1, 2, 3 m--18\({}^{\circ}\); 4 m--12\({}^{\circ}\) and 5, 6, 7 m--6\({}^{\circ}\).