No cheating now Mr. Spock. I saw mention of surface scrubbing which a lot of folks forget in that information but I didn't see the vacuum effect on chimneys and in attics due to gable end venting. Nor is any mention made of back pressure effects on heat exchangers in various heating devices that get vented into things they should avoid. All in all that is a fairly nice depiction of things, where it gets complicated is when actual building construction is a bit (shall we say) lacking in care. Nothing like a good thermal imaging system to find those gremlins.