## 2 Materials and Methods  
It is important to note that the regulation of safety issues in the field of monitoring nitrogen dioxide is complicated by the fact that there is no consistent approach in the world: different countries validate different values of maximum permissible concentrations and the methods for calculating safe zones from exposure to toxic gases differ significantly. Regarding comparative analysis, the statutory conditions of the Russian Federation and Australia were selected, caused by the association with the high competence of Australian blasting companies around the world. In Russia, the maximum permissible concentrations of hazardous substances are established by the Hygienic Standards GN 2.2.5.3532-18 \"Maximum Permissible Concentrations (MPC) of Hazardous Substances in the Air of the Working Area\" [38], and in Australia, the employer's responsibilities to prevent the harmful and dangerous effects of hazardous substances are regulated in the \"Workplace Exposure Standards for Airborne Contaminants\"(Adoption Date: 27 April 2018) [39] in accordance with the Work Health and Safety Act (WHS) [40] and the Work Health and Safety Regulations (WHS Regulations) [41]. As a consequence, it is worthwhile to note that in Russia, the maximum permissible concentration of nitrogen dioxide is below and equals to 2 mg/m\({}^{3}\), and in the Australian statutory conditions, the maximum permissible concentration equals to 9.4 mg/m\({}^{3}\). There are a number of methods to reduce emissions of gases generated after blasting operations, based on neutralization with various solutions, fixant additives and foams, but almost all of these methods are used to reduce emissions of sulfur oxides and carbon monoxide. Most of the methods for reducing nitrogen oxides are aimed at cleaning exhaust gases in metallurgy. In open pits, due to low costs, the methods of water stemming and pre-wetting of the block where the explosion will occur are most often used to form nitrous acid which settles on the ground. However, this method does not meet the requirements when there is a significant amount of toxic gases. It is of importance to note the use of foam-gel stemming, which is made from 1.5-3.0% aqueous solutions of foam-gel-forming substances, and the modus operandi, of which does not differ from the previous one. In this case, the centers of neutralization of toxic gases in the atmosphere are small drops and bubbles of foam gel, which, in comparison with other methods, requires fewer components in preparation due to the fivefold foaming process [42]. Another topic includes researches related to methods of improving the quality of stemming in a borehole, because its use ensures the completion of secondary reactions and reduces the amount of gases released after the explosion, for example, the use of bend as stemming [43] or the using of pneumatic compression in a borehole for a length of 30-40 cm for stemming made from crude mineral salt [44]. Technologic methods of reducing the initial parameters of the dust and gas cloud are used in open pits, which are aimed to reduce the output of explosive detonation products from the drill hole collar: high face blasting in a compressed structure, blasting in boreholes with air gaps and using active stemming and funnel initiation of an explosive in a borehole. However, these methods have a number of disadvantages: the use of active stemming is always closely associated with additional consumption of explosives; drilling and loading equipment does not always meet the requirements for blasting on high benches; it is difficult to mechanize such processes as the formation of charges with air gaps, and there are also restrictions on the use of this method in crumbling rocks and if there is a field water-cut [45].