I been doing some startups on some Natural Gas fired Power Flame burner type steam boilers recently and have been have a little trouble getting real low CO readings with my electronic Bachrach kit. I'd like to see zero PPM with CO2 about 9.5 or more and 02 at 4 or less. Sometimes I seem to have trouble getting less than about 25 PPM CO. I guess I can live with anything under 50 as long as CO2 and O2 are acceptable. Of course, with High/Low fire or modulating burners you often have to sacrifice a little on one end to get better readings at the other.
I wonder what numbers some of you guys might be looking for or any other thoughts you might have on the subject?