I had to replace my 4” duct fan. It was making all kinds of noise, but I don’t think the airflow was what it was supposed to be even though the fan was working after I pulled it. Put in a new 6” filter and fan and it’s dead silent now and moving much more air. The smell of the tent has improved as well. There was kind of a musty smell going on, but that’s all cleared up and these ladies are looking great!