A breath analysis device is described which minimizes mixing of gases between one section of a breath and another section of breath. In particular for example, when sampling and analyzing the end-tidal section of exhaled gas, the system may avoid mixing that can occur inside the device, between the end-tidal sample and the gases before and after the end-tidal sample. The system accomplishes this with an ultra-low uniform cross section fluid pathway, which includes componentry with ultra-low dead space.
