Figure 4
From: A novel application of capnography during controlled human exposure to air pollution
![Figure 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2F1475-925X-5-54/MediaObjects/12938_2006_Article_197_Fig4_HTML.jpg)
Unexpected zero shift for one test out of eight. Screenshot of WinDaq window showing trend capnography tracing for the EXP#1 (left side) and EXP#2 (right side) for the subject who had the particle delivery/CO2 removal mask incorrectly positioned during the EXP#2 that caused CO2 re-breathing.