I have done some little adjusting on this and being able to see the 2nd and 3rd chamber helps so much I really dont know how you guys who buy these with no windows can adj. them? Up-date, my unit is home made and up draft,would not have any other, the door on bottom is 1rst. chamber the middle whole is 2nd. where most action happends and the blue flame is 3rd, Seeing this is almost a thing you have to have. Heck just turning my air adj. just a small amount will change the flame ALOT!. Hope this may help some of you with projects,