I aint got any seal on mine apart from a good ol layer of creosote/tar/smoke/liquid rundown whatever it is buildup. Works real good and dies off as soon as shut the air vent. Mind you mine is a real ugly UDS with no paint or nothing so the rundown actually stops it rusting a bit But the Weber lid fits perfect coz I took out a wedge from the drumtop and welded it up real good. I reckon thats the secret, Well actually welded it pretty darned rough and spent some time with a grinder re doing it and making it look good to tell the truth. 1st welding attempt!