Oren wrote, on Sun, 31 Aug 2014 12:33:23 -0700:

I think the only ventilation is what these little openings provide.
https://c2.staticflickr.com/6/5574/1...ef7ef803_b.jpg

That looks like a bathroom ventilation fan to extract moisture from
the bathroom. It's mounted in the ceiling in the bathroom? Going out a
soffit vent...

Yes. That was connected to the bathroom. I hadn't even known that
but when you said this, I turned it on, and then went to the attic
two floors up, and noticed that it was humming. So, you know what
it is, better than I do!