End-tidal carbon dioxide (EtCO2) can be measured by colorimetry and capnography. Colorimetric devices provide continuous, semi-quantitative EtCO2 monitoring. A typical device has the following three color ranges:
Purple—EtCO2 is less than 0.5%
Tan—EtCO2 is 0.5–2%
Yellow—EtCO2 is greater than 2%








