Comment by idiotsecant

Wonder no more. There is mountains of research on this for occupational health concerns. As long as your fan is <70dB there is virtually no risk to your hearing.

There might be some to your dog, on the other hand. Anecdotal, but my dog went deaf pretty early and he sleeps in a room where I run an air purifier all night. Not sure if there is correlation or causation there but that's my little anecdata.