House vents

So...how dangerous is it to have your dryer venting into the attic? We are renting this house. Various appliances come with it, including a washer and dryer. Well, the washer is from about 1982 (and is now leaking water when it drains--despite replacing the washer in the hose). The dryer was probably older than me, and recently the motor went out, so our landlord bought a new one. But unlike the old dryer, we're having to run the loads several times through to dry them. I did check the exhaust hose to make sure it wasn't plugged when we switched dryers. It seemed okay--and since it goes straight up, I figure that gravity would bring stuff down to the bottom, right? 

So anyway, I'm talking with my sister today. She and her husband own--and therefore repair--rental property. She asked me where exactly the dryer vents to. And I had no idea. So I just checked. Through the wall behind the dryer into the garage, and then straight up into the ceiling. I went outside. Aside from a couple of sewer air pipes, THERE IS NO EXHAUST ANYTHING IN THE ROOF. Or on any walls.

So...the stove hood...and the furnace...and the dryer...and the bathroom fan...all go--where??

This is also the house with the shower lined with masonite and linoleum.

Um...maybe moving isn't such a bad thing. I just hope the place holds itself together until after we're gone.