As a biological waste media, it has many advantages over other more invasive approaches. It can be given at will with a large volume of potential sample, it has a high level of patient acceptability, it is non-invasive, sample collection is very quick and it is potentially possible to analyse the sample in almost real-time. This has made breath analysis a target focus for many groups working on a broad range of diseases. Previous studies, by the investigators group and others have shown that breath analysis can be used to identify patients with irritable bowel diseases, hepatic encephalopathy, cancers (specifically colorectal and breast) and respiratory infections (such as tuberculosis).