## 5 Conclusions  
This article analyses the scope of practical application of metal nanooxides with view to needs of the rescuers during uncontrolled releases of hazardous substances. In the testing, use was made of commercially available MgO-TiO\({}_{2}\) sold under the trade name of FastAct (FA). Its proprieties were compared to selected sorbents that are commonly used by rescuers during actions, generally marked as CDE (granulated sorbent based on calcined diatomaceous earth), PC (polyacrylamideamide copolymer), EP (expanded perlite). It can be seen clearly that the nanocrystalline MgO-TiO\({}_{2}\) specimen (FA) does not exhibit higher maximal mass sorptivity S\({}_{\rm w}\) or maximal volume sorptivity S\({}_{\rm v}\) in relation to sorbents used so far during rescue operations. Much better S\({}_{\rm w}\) results were obtained for expanded perlite (EP) and water activated polyacrylamide copolymer (PC). As compared to MgO-TiO\({}_{2}\), the S\({}_{\rm v}\) parameter was found to be better not only for water-activated PC but also for calcinated diatomice earth sorbent (CDE). Considering also the significantly higher prices of nanooxides (min. 50 euro/kg), their use as sorbents of hydrocarbon substances seems to be highly unprofitable for the time being. The majority of sorbents currently used by fire services have a price much lower than 5 euro/kg. Furthermore, despite a well-developed surface structure FA does not assure protection from evaporation of sorbate from its surface. Measurements with n-heptane and ethanol have shown that even at a mass ratio sorbent:sorbate that is far from maximal sorptivity, the weight loss of sorbate from FA is similar in magnitude and even greater than the weight loss recorded for evaporation from the surface of pure sorbates (n-heptane and ethanol). This confirms the presumption about the decisive role of physical sorption on MgO-TiO\({}_{2}\) surface in the case of hydrocarbons and monohydric alcohols. However, increased evaporation could also result from the very large specific surface area. The increase of a fire hazard was also confirmed by comparative studies of ignition temperature of pure p-xylene and in configuration p-xylene:FA and p-xylene:CDE. At a mass ratio of 1:2 the vapor ignition temperature was found to decrease both in the case of p-xylene absorbed by CDE and FA. This proves that this neutralizer is not appropriate for trapping hydrocarbon vapors and alcohols from the air, which constitute the biggest group of chemical fire hazards in industry and in transport. Studies have pointed to a considerable susceptibility of nanooxides to ageing, which is of particular importance for the storage of those compounds. As a result of the large proper surface of MgO-TiO\({}_{2}\), the rate of water absorption is 12-fold bigger than for the hygroscopic CaO. On the other hand, hydrophobized ABC powder (Extinguishing powder dedicated for ABC group fires (solids, liquids, gases)) with a monoammonium phosphate content of 90% absorbs water 37 times slower than FA. The energetic effect of the neutralization process by FA during unconstrained pouring does not assure a much better safety of rescue operations than, for example, in the case of NaHCO\({}_{3}\). To allow the process to take place relatively quickly mixing is essential, as fine and hydrophobised nanocrystalline remains at the acid surface, reacting slowly. In addition the mixing process causes a two-fold increase in temperature (\(\Delta\)TMgO-TiO\({}_{2}\) = 46.0 \({}^{\circ}\)C) than was the case for the reaction with free pouring without mixing. Studies have shown that in the case of neutralization including mixing in the mass ratio of MgO-TiO\({}_{2}\) to H\({}_{2}\)SO\({}_{4}\) of 1:2, the temperature increase \(\Delta\)T can be as high as 170 \({}^{\circ}\)C, consequently posing a much more material risk of burns due to careless operation of the rescuer than is the case for NaHCO\({}_{3}\) at the same ratio (\(\Delta\)T\({}_{\text{NaHCO3}}\) = 74.8 \({}^{\circ}\)C).