Most of sensor vendors are utilizing essentially the same technology using the Infrared spectroscpy. Unlike common lab application, the devices do not scan over the wavelength or freaqucncy range since the absorption peak position of CO2 is well knon. This makes the instrumentation a whole lot simple and rugged. Because the central units come in module such that a user can configure a system for his/her own way. The other important point is that we provides a hand-held device with excellent performance. The US is clearly going behind many Asian and European countries in many araes. The science education in US seems very weak.
Optical spectroscopy, Neutron/gamma-ray spectroscopy, Numerical simulations based on Density Functional Theory, molecular dynamics