There are two standardized methods for the presentation of odour sample to the panel: forced choice and yes/no method [37,38,53]. In the forced choice method, two or more sniffing ports are used; the odour sample is presented at one port, and neutral air at the other port(s). In this case, the examiners have to compare the different presentations and to choose the port from which odour exits. In the yes/no method each examiner sniffs from a single port and communicates if an odour is detected or not. Odour samples diluted with neutral air or only neutral air can exit from the sniffing port.