marengnr t1_j1e5fb4 wrote on December 23, 2022 at 5:15 PM

Used to run oil fired boilers. CO was 0%. It was monitored, but if there was CO, that meant insufficient O2, which meant incomplete combustion, which meant $$$ going up the stack rather than making steam.

We didn't monitor NOx.

genericTerry t1_j1fnrru wrote on December 23, 2022 at 11:45 PM

Excess oxygen is also $$$ going up the stack as your heating up air as well as the combustion products.

paulHarkonen t1_j1hxkvz wrote on December 24, 2022 at 2:26 PM

Not to anywhere close to the same degree. Excess fuel consumption is way more costly than heating up a little bit of extra air.

Obviously you want to run as close to stoichiometric as possible, but since we are only human, running a bit lean is less expensive than running a bit rich (all other factors being equal).