Fig. 1. Schematic of the breath isoprene analyzer

Fig. 2. The fitting of the data of typical ringdown decay waveform under vacuum
(a) The typical ringdown decay waveform under vacuum; (b) The fitting of the data in Figure 2 (a)

Fig. 3. Ringdown signal stability under six average times
(a): Average time is 2; (b): Average time is 16; (c): Average time is 64; (d): Average time is 128; (e): Average time is 256; (f): Average time is 512

Fig. 4. Evaluation of the ringdown baseline stability of the breath isoprene analyzer

Fig. 5. The breath isoprene analyzer shows good reproducibility and fast response

Fig. 6. Linear response to various standard isoprene concentrations measured by the bseath isoprene analyzer

Fig. 7. Comparison of absorbance