[Bldg-sim] CO2 sensing in practice

[Chris Yates]

Hi

I've just received some tech info on CO2 measurement (NDIR) and was 
wondering what accuracy was realistic for these devices in practice. 
I've heard of calibration problems with CO2 and want to model it in a 
way that it will respond in the real world.

OK... A suppliers device measures the 0 - 2000ppm range and returns a 
signal of 0 - 10V range. ASHRAE 62.1 IAQ method stipulates limits in the 
range of 0 - 2000ppm as acceptable health guidelines depending on where 
your building is - great. However, Appendix C also suggests that if CO2 
is used as a surrogate for occupant odour, odours become apparent as low 
as 750ppm. Therefore, it would be best to have the detectors come on 
before this.

The signal in this range will be less than 2 Volts. Therefore, is it 
unrealistic that my model "senses" levels of CO2 in the range 350 
(ambient) - 750ppm?

If not, are there more accurate commercially viable alternatives?

Best regards

Chris Yates