positive pressure

good day think tank members…chris C made this statement in a former thread:
Do not common-vent natural draft with appliances that use a positive-pressure draft. Remember that the draft inducer fans in medium-efficiency furnaces don’t put the vent under positive pressure.

well i believe chris and i dont get it, seems to me that this would be a positive pressure situation so i am evidently confusing some details. if anyone would care to elaborate on this situation and explain what would be a positive draft scenerio…that would be great.

seeking the truth in MN
(aka mike in MN)


oops sorry chris…i meant to say ‘i believe chris (is correct)’…and i (mike) dont get it. sorry about that

thanks troy…excellent input which i plan to study in depth
mike in MN