A novel device for the study of antimicrobial activity by vapour contact of volatile substances have been designed. This "big size" system, made up in inert acrylic material, is furnished with a fan and a hot plate with the aim to have a quick evaporation of volatile substances. It is able to contain fruits or other food products under controlled atmosphere and it can simulate real condition of storage or as well real condition of food pre-treatment by antimicrobial volatile substances. Such system is suitable to perform both in vitro (disk diffusion test) and in vivo (exposure and testing of food products) experiments. To shed light on the behaviour of this chamber the concentration in the head space of several substances have been monitored by GC-MS analysis during the time. Both single (mono-terpene compounds) and mixture of terpenoids have been studied. Different behaviours have been founds depending on the starting molecules studied. Limonene, myrcene and eucalyptol, in single standard experiment, show a similar shape of head space concentration curve versus the time: the concentration increases at the beginning, then reaches a maximum and decreases until it reaches a plateau. In contrast linalool shows a head space concentration curve constant during the time, whereas mixtures of terpenes like myrcene and linalool show a concentration curve of vapour phase in agreement with Raloult's Law. The experiments carried out with Essential Oils (EOs) shows that in our system only more volatile fraction of EOs compose the vapour phase.