I have mine in my audio rack, and it is open on the sides and front, but the back and top have very little clearance. I'm not using any of it's internal amps to drive any speakers, but it still gets pretty warm, and my old RX-V1600 got pretty warm to when I was using it's internal amps. When I had my RX-V1600's internal fan set to auto it never came on, so I just set it to run all the time, but the 1800 doesn't have a fan. Unless it's getting super hot, I wouldn't worry about it, I'm sure it doesn't get quite as hot as some Onkyo models.