## 2 State of the Art  
Ventilation in underground mines can be a costly and complex process, as it depends on factors such as the mining technology and the geometry of the mine. Additionally, local air quality can fluctuate, which poses a risk to miners. Ensuring the safety of underground mining crews is of utmost importance in mining operations. This is reflected in various regulations that impose restrictions on human work in excavations where working conditions may pose a risk to workers' health or safety [11; 12; 13; 14; 15]. Examples of such regulations include legal acts that limit the temperature or the concentration of harmful substances in the workplace. These acts also define different types of natural hazards that may affect workers in underground mines [16]. Adhering to these regulations and taking appropriate measures to mitigate risks is crucial for maintaining a safe work environment for underground mining crews. As mining operations move away from the main underground excavations and intake sharts, the risk of natural hazards in underground mines increases [17; 18; 19]. Of these hazards, the atmospheric and gas hazards pose the greatest danger. Harmful gases can enter the mine atmosphere naturally, such as methane and hydrogen sulphide, or as a result of technological processes, including carbon monoxide and nitrogen oxides. In recent years, scientists have been analysing the impact of nitrogen oxides (NOx) in underground mines, as they are one of the most harmful gases present. In general, NOx are composed of nitrogen oxide (NO) and nitrogen dioxide (NO\({}_{2}\)) [20; 21]. All NOx gas hazards in underground mining operations can be grouped into those that appear naturally or those that appear due to technological processes. The natural sources of NOx in an underground mine are the emission of gas from the rock mass or the oxidation of nitrogen from the atmosphere. However, it should be noted that the largest volumes of NOx are generated in processes related to the technological cycle of the mine: welding work, blasting work, and, above all, diesel-powered machinery [2]. The primary source of NOx in the mine atmosphere is technological processes, specifically the operation of diesel machinery [22; 23]. One of the main sources of harmful compounds that are released into the mine atmosphere is diesel-powered machinery. Diesel engines generate many chemical compounds in liquid, solid, and, most importantly, gaseous states. The most important of these are sulphur dioxide (SO\({}_{2}\)), carbon monoxide (CO), carbon dioxide (CO\({}_{2}\)), hydrocarbon compounds (CH\({}_{x}\)), nitrogen oxide (NO), nitrogen dioxide (NO\({}_{2}\)), and solid particles [24; 25; 26; 27; 28; 29]. According to [PERSON] and [PERSON] [30] and [PERSON] [31], NOx is a harmful air pollutant that can have significant impacts on both the environment and human health. Both monoxide NO and dioxide NO\({}_{2}\) are odourless gases. Nitrogen monoxide is a colourless gas, while nitrogen dioxide at a certain concentration can take on a brown colour [32; 33]. In the exhaust of a diesel engine, the share of nitrogen oxides is about 90% NO and about 10% NO\({}_{2}\)[34]. NOx can be a danger to human health, particularly for people with respiratory problems or heart disease. Exposure to high levels of NOx can cause irritation of the eyes and throat, coughing, shortness of breath, and reduced lung function. Long-term exposure to NOx can increase the risk of respiratory infections and chronic lung diseases [35; 36; 37; 38]. The more toxic gas is nitrogen dioxide [39], which at 1.5 ppm already causes respiratory problems, while at 5 ppm it leads to a drop in blood pressure. When the NO\({}_{2}\) concentration reaches about 200 ppm, it can result in human death [40]. Due to the negative influence of NOx on humans, it is important to monitor the concentrations of nitrogen oxides in underground mines. However, it is even more important to predict the NOx emissions from LHD vehicles and heavy transport trucks, depending on individual working modes.