While CO2 is not toxic in the same sense as CO, it has wide ranging significance to the lives of all of us, in our life processes and as a prime source of global warning.  It is used in industries of all kinds, and we supply monitors using the infrared principle for concentrations ranging from 1000 ppm to 100%.  It can also be detected using thermal conductivity at the higher levels. Concentrations above 5000 ppm are considered of concern from the breathing standpoint.