Gentlefolk,

One stove vent actually vents to the outside. There's a couple of
semicircular metal flaps at the bottom of the ductwork that seal it
off when the fan is off, but they flip up when enough pressure has
been built up from below, opening the vent and letting the nasty fumes
out.

Problem is that the flaps and the ductwork are greasy and tend to
stick in the 'up' position. It's not much trouble in the summer, but
in the winter, cold air pours in from the outside. I take off the
aluminum filter, then pick and pry with a pancake flipper until the
errant flap comes down.

I attempted to clean 'em with degreaser but it's pretty hard to reach
up there. I'd really rather not take down the entire vent from its
ducting if there's a better way. Any ideas?

Best -- Terry