## 4 Discussion  
The statistical analysis demonstrates high deviation of the measured values gained from different devices. According to the results obtained, humidity has an impact on the measurement accuracy. Moreover, the Fisher criterion demonstrated that the concentration of most components had a clear similarity with the reference measurements (Table 3). Considering each marker separately, namely for SO\({}_{2}\), the f-value is 1.54, and for NO it was 3.09, confirming the null hypothesis with a significance of 0.01. Nevertheless, for NO\({}_{x}\), the Fisher criterion was 6.46, for O\({}_{2}\) it was 6.21, for CO it was 4.69, and for NO\({}_{2}\) it was 65.9, thus rejecting the null hypothesis. It is worth noting that the concentration of NO\({}_{2}\) cannot exceed the concentration of NO\({}_{x}\). In addition, the statistical significance of 0.01 testing through the t- and ANOVA methods demonstrated that O\({}_{2}\), SO\({}_{2}\), and NO\({}_{x}\) values for Inspector 500 and AMS showed no significant deviation, but this was not so for NO, NO\({}_{2}\), and CO (Table 4). The controversy of the results gained for O\({}_{2}\) is demonstrated by the fact that the values could be corrected by mathematical tools, however, more measurements are needed to accomplish this goal. In the values for NO\({}_{2}\), the reason for these significant deviations can be explained by the mistakes in the measurement and data computing processes. According to the comparison of the errors, the highest among all the components are for NO\({}_{2}\), CO, and NO, which were caused by the water particles' presence in the  
Figure 14: Comparison of statistical values for SO\({}_{2}\), NO\({}_{x}\), O\({}_{2}\). Figure 15: Errors for concentration with POLAR. probe firstly, and secondly due to systematic error, which is explained by the gaps in the graphs (Figure 10). In addition, the automated monitoring system (AMS) has the auto-calibrating subsystem, which is automatic. Due to that, the AMS periodically cleans and sets itself by calibrating gas. However, the calibrating system is not monitored as well. Therefore, the error can be caused by the system. Moreover, a high error like for NO\({}_{2}\), namely 733.26%, can lead to consequences which can worsen conditions of companies. An enterprise where stationary sources of emissions are registered pays an environmental fee annually, according to the maximum permissible emission standards. However, according to environmental monitoring, if these standards are exceeded, then fines are imposed on enterprises. Therefore, the consequences of such errors carry additional financial costs for the enterprise in the form of fines. As well as the consequence, an incorrect decision may be made within the framework of process control. On the other hand, the difference between the CO readings is caused by the fact that the measurement range of both devices differs. In addition, the RMD1 and RMD2 for both devices varied and reached 38% of the arithmetic mean at the factory error of 25% for devices built into the SOLER SGK-510. This fact indicates the presence of various factors that introduce a strong measurement error. On the other hand, it is possible to increase the accuracy of measurements by using linear coefficients, and displacement using the least squares method (Figure 16). Thus, the relative error in measuring the concentration of CO can be reduced to 0.0017%, but the [PERSON] criterion in this case is reduced to 13.86, which indicates that the dependence is approaching real measurements. In the case of NO, the error approaches 0%, and the Fisher criterion is 478.16, which also leads to the rejection of the null hypothesis (Figure 17). Figure 16: Adjusted dependence of CO measurements of AMS. Figure 17: Adjusted dependence of AMS measurements. Therefore, the use of a linear coefficient to correct the readings is impractical and requires further observation. Moreover, in order to increase the accuracy of this system, it is also necessary to use a multicomponent analysis of sample properties.