burners the standard blue flame burner currently used in commercial gas space heaters produce levels of nitrogen dioxide in the order of 15 20 ng joule whereas a low no x burner according to the present invention can produce levels as low as 1 ng joule the object of the testing was to produce a means of defining the operating conditions of the low no x burner to effect a predetermined emission of nitrogen dioxide the australian gas association procedures were used to measure appliance emissions in a form relative to the burner output all no x levels were measured using monitor labs nitrogen oxides analyzer model 8840 and are therefore subject to the accuracy and inherent limitations of such an instrument the nitrogen dioxide level can be expressed in units of nanograms per joule ng j which in turn will relate to room size this will indirectly control the no 2 levels within a room where an unflued appliance is being operated the levels measured within any given room will therefore vary on the size of that room the ventilation the content of the room the absorption of nitrogen dioxide into walls and the background level of no 2 accordingly because of this variability a fairly complex model was required to provide an accurate account for the level of no 2 within a given room to evaluate the levels of emission the burner was mounted to a rig beneath a sampling hood the background.