Yum-Yum- looks like some might-ty fine scraping for ya. I think you'll be able to fill a 40 gallon trash can. Talk about "shag-nasty". You'll have to use your real small guy to get inside that duct. Those forward thinkers who built it even installed what looks like a clean out door at the top of the vertical shaft on the roof. The other good thing about it is - once it's cleaned - it won't look that bad for another 15 years. It looks like an old IHOP.