Chemical sensors are tools able to detect organic and inorganic molecules in the three states of matter with different mechanisms of interaction. Each molecule interacts in a different way with sensing materials, producing dissimilar changes in its intrinsic properties. In recent years, chemical sensors have been widely used in arrays for devices known as electronic noses (ENs). They showed great potentiality to be applied in various fields, like health, environmental monitoring and food quality and identity. One of these devices, called Small Sensors System (S3) produced by NASYS, a spin-off of University of Brescia, is equipped with innovative chemical sensors that analyse volatile compounds. They are designed and constructed at SENSOR Laboratory (University of Brescia) and are different from the other metal oxide semiconductor (MOX) sensors available on the market because of their nanometric dimensions. This brings numerous advantages since nanomaterials have an extraordinary length-to-width ratio, that enhances sensing capability and long-term stability for prolonged operation. In addition, the three-dimensional network formed by the nanowires increases the adsorption surface and the catalytic activity, improving the response and decreasing the threshold up to few ppm concentrations. The ability to connect to Internet makes S3 an Internet of Thing (IoT) device. This allows to send and storage data in the cloud and to use S3 remotely. Indeed, S3 has a dedicated user-friendly Web App whereby users can analyse data on-line using different techniques, from univariate and multivariate statistical analysis to Artificial Neural Networks. S3 system has shown the capability to be a useful tool in agri-food field. Among the whole applications, it has been successfully used to recognize the authenticity of food and to individuate food pathogens and microbiological contamination as described in the following sections.