[Stoves] Making testing equipment for CO and O2

[Tami Bond]

Hi all,

I *think* that Nernst cells are the same principle as the 
electrochemical cells used in most inexpensive CO sensors. However, some 
of the electrochemical cells are corrected for interferences (measuring 
one gas as another).

I can see a need for measuring O2 in the exhaust of a chimney stove, or 
the outlet of a non-chimney stove. O2 is available in most combustion 
analyzers. I'm much more in favor of measuring CO2 because (1) it can be 
directly traced to the fuel and (2) if you have a lot of excess 
air/dilution, as you do above a non-chimney stove, the O2 quickly 
approaches atmospheric content and the calculation of excess air becomes 
very sensitive to small differences. The calculation of excess air is 
fairly robust if you are measuring 5% or 10% O2, but not very robust at 
all if you measure 19% O2. That's why we like to measure CO2 directly, 
and then the CO/CO2 ratio is better known. We get our CO2 sensors 
(infrared) from Telaire and they do take some wiring and calibration. 
These inexpensive CO2 sensors have been available only in the last ~5 
years, and they are slowly making their way into combustion analyzers. 
O2 is still far more prevalent, but again, I think it is much less 
appropriate to stove applications.

Tami

*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
Assistant Professor
Arthur & Virginia Naumann Endowed Faculty Scholar
Dept. of Civil & Environmental Engineering
University of Illinois, Urbana-Champaign
Newmark Civil Engineering Laboratory, MC-250   (01)217-244-5277
205 N. Mathews Ave., Urbana, IL 61801   USA    fax/217-333-6968