it vibrates the whole 'bator. I have a Hovabator 1602N and have done three successful hatches in it without a fan, but hatch rates were slightly under 50% (two shipped eggs, one local). I could tell that there were hot spots, though. So I got a little knee-jerk the other day and bid on some marans eggs even though I had no plans to hatch this winter. (but I miss my marans hen that was taken by a fox this spring, I know you all get it! Emotion! Chicken math!) Then I rounded it out with some Isbar eggs. I KNOW I can get a decent hatch just going still air like I have before, but I'd sure like to improve my percentage. So my husband said that he could tackle the fan thing. He did, but not ideally. He had trouble finding a 2 wire fan and what he ended up with is a 4" that he had to hang from long screws off of the top of the bator. I love what it's doing for the temp and it doesn't seem to be affecting humidity much, but it is noisy and it vibrates my incubator. Just a slight buzzing on the styrofoam if you put your hand on it, but it's there. The eggs need to go in today. They've been resting for 12 hours and I need to just decide whether I'm going to run this thing or not. Thoughts? It feels like a real risk vs. benefit analysis.....a) the hot spots are worse or b) the vibration is worse. :/ I wish that I had had time to get the one from Incubator Warehouse but I just didn't. Like I said, spur-of-the-moment decision to hatch these littles.