Odour assessment with Electronic nose
E-nose, more correctly called IOMS (Instrumental Odour Monitoring System), is used to monitor odour continuously and assess the nuisance caused by malodorous sources.
The system is equipped with a range of different sensors, mounted in easily replaceable modules. Many types of sensors are used, from metal-oxide semiconductors (MOS) capable of detecting both organic and inorganic molecules, specific electrochemical sensors (EC) used to detect single pollutants such as ammonia and hydrogen sulphide, selective photoionization detectors (PID) for unsaturated compounds (e.g. aromatic hydrocarbons, olefins, carbonyl compounds) and many others.
Electronic noses must firstly be calibrated to the characteristic odours of the various sources to be monitored, in order to quantify them and give the response in odour units.
This calibration occurs in the following stages: odour samples from the sources to monitor are collected on site in Nalophan bags by odour sampling device (vacuum pump) for ambient air, and their appropriate calibrated dilutions are subjected to olfactometric analysis (human panel) to define the odour concentration of the sample according to UNI EN 13725:2004.
The electronic noses are exposed to the same samples and their calibrated dilutions to acquire an odour fingerprint, after which they can be calibrated to recognise different odour sources with the response calibrated in odour units (ouE / m3).
The electronic nose, installed at the sensitive receptor, continuously records the presence of odours, recognises their origin and specifies their intensity in odour units. In this way, from the ratio between the number of odour events and the total time monitored, the frequency of odour episodes is obtained and is related to the assessment of nuisance level, and therefore to the normal tolerability of the exposed population.