## 2 Experimental Part
### Research Methodology  
In the studies, a change in concentration of vapours of tested substances was performed in the time function after subjecting their vapours to the action of overhead water curtain in the research chamber The water jet was played with the use of a garden nozzle having a diameter of \(\Phi=1\) mm. Within the studied efficiency range of curtains, the jet was characterised by droplet diameter within the range of 270 \(\upmu\)m \(<\) \(d\) \(<\) 247 \(\upmu\)m, which by definition classifies it as a fog stream (\(d\) \(<\) 1 mm). It was assumed that the average value would be \(d\) = 260 \(\upmu\)m. The characteristics of water jet droplet distribution used in our studies were presented on Figure 1A.  
To study average droplet diameters the AWK Drop Spectrum Analyzer made by Zaklad Elektronicznej Aparatury Pomiarowej (Electronic Measuring Equipment Plant), K\(\upmu\)K in Warsaw (Poland) was used. The analyzer allows the determination of average diameter of droplets in the range from 0.5 to 3000 \(\upmu\)m. The device scheme is shown in Figure 1B.  
The obtained droplet size has both a large sorption surface and an acceptable resistance to windy weather. The water jet played from the nozzle has a similar droplet distribution parameter conforming to modern turbine extinguishing system technologies (e.g., ZIKV _Turbo-Loscher II_ vehicle with an average jet droplet distribution of \(d\) = 375 \(\upmu\)m).  
The tests were carried out in a tight measurement chamber having a volume of 322.4 dm\({}^{3}\) (476 \(\times\) 676 \(\times\) 1002 mm) as presented on Figure 2. The fog stream came from a single nozzle provided at the centre of the upper chamber wall (7 at Figure 2). Water was flowing through the rotameter, with a precision of up to 1 dm\({}^{3}\)/h (4 at Figure 2).  
As regards acetone and alcohols, the research atmosphere was generated by unconstrained evaporation of samples from Petri dishes (8 at Figure 2) with a diameter of 9 cm to simulate conditions of uncontrolled release of a substance within a limited storage facility. To achieve a representative number of research trials characterised by different initial concentrations in the chamber, the evaporation times of samples were made to differ. In the case of ammonia, the gas was delivered from a cylinder (5 at Figure 2). In order to check the reproducibility of the results, at least two measurements with similar concentration values were performed.  
In addition to selected substances, tests were also carried out on the dependence of the rate of absorption constants on the intensity of spraying (25 dm\({}^{3}\) h\({}^{-1}\leq q\leq\) 95 dm\({}^{3}\) h\({}^{-1}\)). The water temperature used in the tests was in the range 283 K \(\leq T\leq\) 295 K. Concentrations of acetone, ethanol, 1-propanol, and 1-butanol were measured with the use of an MSA Sirius multisensory appliance with the use of a photoionisation detector (2 at Figure 2). On the other hand, for methanol (mainly due to excessively high ionisation potential), use was made of a sensor of catalytic combustion. The indicated computational values were in each case multiplied by the appropriate calibration coefficient.  
Figure 1: **(A)** Characteristics of droplet distribution of water stream used in tests. Nozzle with a diameter of \(\Phi\) = 1 mm; d—average droplet diameter; X—distance from the curtain centreline. **(B)** AWK Drops Spectrum Analyzer scheme: 1—probe, 2—transmitter, 3—measuring space, 4—receiver, 5—electrochemical arrangement, D1, D2, and D3—adequate size of droplets.  
Figure 2: Diagram of the research stand: (1) draining valve, (2) gas analyser, (3) recorder, (4) rotameter, (5) ammonia cylinder (in case of ammonia), (6) measurement chamber, (7) spray nozzle, (8) Petri dish (for acetone and alcohols), (9) water supply.