The air–fuel ratio is a crucial parameter in internal combustion engines that affects optimal engine performance, emissions, fuel efficiency, engine durability, power, and efficiency. Positive pressure ventilators (PPVs) create specific operating conditions for drive units, characterized by a reduced ambient pressure compared to standard atmospheric pressure, which is used to control carburetor-based fuel supply systems. The impact of these conditions was investigated for four commonly used PPVs (with internal combustion engines) in fire services across the European Union (EU), using a lambda (λ), carbon dioxide (CO₂), carbon monoxide (CO), and hydrogen carbon (HC) analyser for exhaust gases. All four ventilators were found to operate with lean and very lean mixtures, with their lambda coefficients ranging from 1.6 to 2.2. The conducted tests of the CO₂, CO, and HC concentrations in the exhaust gases of all four fans show dependencies consistent with theoretical analyses of the impact of the fuel–air mixture on emissions. It can be observed that as the amount of burned air decreases, the values of CO and HC decrease, while the concentration of CO₂ increases with the increase in engine load. Such an operation can accelerate engine wear, increase the emission of harmful exhaust gases, and reduce the effective performance of the device. This condition is attributed to an inadequate design process, where drive units are typically designed to operate within atmospheric pressure conditions, as is common for these engines. However, when operating with a PPV, the fan’s rotor induces significant air movement, leading to a reduction in ambient pressure on the intake side where the engine is located, thereby disrupting its proper operation.

Requirements currently imposed on machine elements are constantly growing. It requires to develop new, advanced machining processes. One of the commonly used finishing process is grinding. The article presents the results of the exploratory research in the process of surface grinding with abrasive multigrain wheels of samples made of Inconel 718. The influence of input parameters was investigated: cutting speed Vc, transverse feed speed Fp, longitudinal feed speed Fw, on roughness parameters (Sa) and the bearing capacity curve. Based on the conducted research, statistical models of the grinding process were elaborated, which allow to select the most favorable processing parameters depending on the required quality of the surface texture.

The article presents the characteristics of the distribution of magnetic flux density inside the machining gap in the magnetic abrasive finishing (MAF). Based on the analysis of the magnetic field in the empty gap and the distribution of forces in the magnetic circuit, the concept of measuring the real value of magnetic induction in a flexible abrasive tool formed in an external magnetic field was proposed. An indirect way of determining the magnetic induction has been described, which has a significant influence on the force acting on abrasive grains in the process of magnetic abrasive finishing. The advantages and the problems of the applied approach as well as the measurement methodology based on the change in the attraction force of the magnetic field elements as a result of the change in the concentration of abrasive grains and the width of the machining gap are presented.