Schematics of exhaled gas setup and data. A. Schematic of experimental setup used to measure exhaled NO and CO in mice. Expired gas from the mouse was sampled from small holding chamber, with an integral stopcock to allow rapid sample switching from ambient to expired air. B. Schematic representation of signals redrawn from actual signals of one individual mouse with airway inflammation. Increased NO (16–18 ppb) and CO (5–7 ppm) is apparent in first 10s of 20s sampling period, when sampling chamber air, as compared with low concentrations of NO (0–2 ppb) and CO (0–1 ppm) in ambient air, pre- and post-sampling of chamber. Additional details are in text.