Iso-max duct fans run extremely quietly. The 6-inch and 8-inch versions also feature a 3-speed controller, allowing you to vary airflow without the purchase of a separate unit. To grow successfully, you’re going to need to create an optimal environment for your plants. Your extractor fan is used to move air to and from your grow area, and will play a role in removing odours and excess moisture, replacing the carbon dioxide that your plants depend on for the process of photosynthesis, and maintaining consistent temperatures. The extractor fan is such a crucial element of any successful grow that it pays to invest in the very best.