Upon setting up a oil burner, why is it neccessary to get the CO2 bang on as a leading factor, why this figure opposed to others? Boiler MI state depending on boiler to be set anywhere from 11%-12% depending on boiler is it ok to set it to 10% CO2 even if manufactures state otherwise as i see on other posts engineers like to set CO2 to 10% opposed to manufactures spec 11%-12% why? and would this make a difference to the running of your boiler and is this exceptable, Thanks for reading