Two use cases: (i) Automation and control of future buildings (economically motiveted) and (ii) diagnosis of "sick" buidlings (technologically motivated).
Fixed infrastructure, semi-mobile (installed for longer periods of time) and mobile sensors and actors.
Temperature, humidity, light, barometric pressure are uncritical, many solutions exist today and are available as low power devices.
O2 - High concentration, difficult to measure
CO2 - Killer app for HVAC, paradigm change in todays HVAC systems: not just moving all air with general vents all the time, but removing at distinct spots at distinct times (exchange on demand) - energy/cost - if pipes can be made smaller, you can build 9 floors in the space of 8 etc.
C02 is typically hard to sense since it is not a reactive gas. There are different sensors based on electrochemical, NdIR or photoacoustic principles available.
Accuracy: ppm are measured, but fluctuations due to occupancy (people) is rather high.
to be defined.