It is not dangerous and losing a bit of hot air thru there won't hurt anything. It is a mastic which Pros use and is probably unavailable to the public. I would scrape it all away and clean the metal with a bit of WD40 to dissolve the remaining goop or use Goo B Gone cleaner. Then lightly sand the metal and use a good quality white or clear bathroom silicone. Simple as that.:thumbsup: