An apparatus for collecting volatile organic compounds from a gas sample such as alveolar breath or room air comprises an exhaust portion having at least a flow measuring device, and a discriminating device for distinguishing between alveolar and non-alveolar breath. The apparatus further comprises a collection portion distinct from and parallel with the exhaust portion having at least a collection component for receiving and concentrating gas samples within a collection chamber and a sampling component having a plurality of sampling devices for receiving the concentrated gas sample from the collection chamber and isolating VOCs contained in the gas sample. The collection chamber is compressible via a drive mechanism for precisely actuating the chamber to draw a gas sample into the collection chamber and circulating the sample to the sampling devices. Use of a drive mechanism enables the exhaust portion to be distinct from the collection portion, thereby mitigating cross-contamination therebetween.
