flame burner configuration the oxygen content is measured by an o 2 analyzer which draws a sample from the venturi 419 in each burner 410 a sample port 494 may be provided in each venturi 419 for this purpose alternatively a sample probe not shown may be inserted into the venturi 419 based upon readings taken by the selected device s mentioned above the primary air chamber damper 428 is then adjusted on each burner 410 to achieve a consistent 02 concentration for each burner 410 although the burner adjustment techniques described with relation to the flat flame burners depicted in fig3 and 4 have been described in detail for adjustments made to the primary air chamber 426 it will be appreciated by those of skill in the art that the adjustment techniques can be advantageously applied to the secondary air chamber 432 as well this is particularly important for the case where the primary air chamber damper 428 is set to the closed condition and flue gas air or mixtures thereof drawn into the primary chamber through passageway 476 when the present invention is employed for secondary air chamber adjustment the vacuum or draft in the secondary air chamber 432 may be measured with a conventional manometer not shown or with a draft gauge 492 in either case the secondary air damper 434 is adjusted to give the same vacuum or draft in the secondary air chamber 432 for each burner 410 likewise a velocity probe not shown may be used to measure the velocity of the air entering the secondary air chamber 432 and or the oxygen content is measured by an o 2 analyzer which draws a sample from the venturi 419.