## 4 Classification of Measurement Methods
### Sensory Analysis  
The human nose has far greater capabilities as a detector of odours. Only the human nose can be used to evaluate parameters such as the character or hedonic tone of the odour. Odour evaluation techniques based on the sense of smell can be divided into two groups, the techniques based on subjective organoleptic evaluations and the techniques based on sensory analyses. Sensory analyses must meet high requirements in terms of the repeatability and reproducibility of the results obtained. In principle, they require an objective and quantitative determination of the odour concentration of all odorous substances together. It is therefore possible to use them for the analysis of odour nuisance. Olfactory is one of the sensory methods. In the literature, a distinction is made between dynamic olfactory (dynamic dilutions), static olfactometry (static dilutions) and separately classified field olfactory (in situ studies) [33; 62]. It relies on the human nose as a detector, but at the same time ensures the repeatability and reproducibility of the results. Olfactory is based on procedures for the controlled dilution of samples/flows of odour-intensive gases with an odourless gas. It requires strict adherence to procedures at all stages, starting with the sensory verification, the sensitivity of the evaluation teams, the method of sample collection and presentation, the recording of the results obtained and the application of appropriate statistical methods to develop them. Using this method, we can, for example, determine the odour threshold of a particular compound, the detection threshold or the concentration of odour units in the analysed gas. This allows us to determine the emission and immission values or to model the spread of odorous substances in the field.  
The olfactometric method is one of the most technically advanced methods for determining odour concentration. In many European countries, it is based on strict procedures laid down in standards [83]. It uses a device called an olfactometer, which allows an objective determination of the odour concentration in a gas sample using the human nose as a detector [84]. The schematic representation of such a device is shown in Figure 2.  
It is a compact system for odour measurement in the laboratory or under mobile conditions. The device enables the automation and precise control of the sample dilution process and the simultaneous presentation of samples to the evaluation team (usually  
Figure 2: Schematic diagram of the measurement of the odour quality of air with an olfactometer.  
four people). It enables precise communication between the team and the computer and automatic statistical evaluation of the data obtained. It enables the immediate presentation of the results. With the help of an odour measurement device (olfactometer), it is also possible to select a representative group of people who can form the evaluation team (panel members) [85]. Table 6 below summarises the most commonly used quantitative methods used by teams of odour specialists in odour assessment. This summary includes approaches that are widely accepted as standard in sensory research and provide an objective and repeatable assessment of odour intensity and quality. These methods are an important element of olfactometric analysis and are widely used both in scientific research and in the technical practise of air quality monitoring.