[MotorBikeLes]

David, you must come from a similar age group to me. I was responsible for conversion to NG of a number of pottery kilns back in 1969.
But back on topic. Most gas analysis equipment has a cell for each gas type, usually of limited life, and either NLA or so expensive you would weep, so it may be just scrap.
I did design a simple gas analyser based on a Bosch Lambda sensor, but it would not work. It had a little fan operated arrangement to draw the gas thro. Subsequent advice suggested it needed some pre-heat, as the internal controlled heater was inadequate on its own. All gas analysers need filtering for soot etc (glass wool in a tube is normal) and usually have a water trap as well.
When I first checked gas kiln atmospheres, I used an Orsat gas analyser. Large glass apparatus, sulphuric acid used to contain the gas sample, caustic potash to extract the carbon dioxide, followed by alkaline pyrogallol to remove the oxygen, and finally alkaline cuprous ammonium chloride for any carbon monoxide.
A 100ml sample of gas was contained, then each test as above removed the "percent CO2", ditto O2 and finally the CO.
Later I had use of a Servomex oxygen analyser (based on oxygen's paramagnetic properties) which sufficed for all burner settings when using air blast burners. Much quicker than the 10 minutes per sample with the Orsat.
Les.