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  • In-line fan, filter & vented reflector

    Created by David Lurie on

    How do you recommend I configuring my air-cooled 600watt grow light with an inline duct fan and a charcoal exhaust filter?

  • Author
  • #206094

    Eric Vinje

    Hi David –

    Air Cooled Set Up 1

    The easiest — and cheapest — way to set-up an air-cooled grow light reflector and carbon filter is to hang the filter before your hood and connect the two using a short piece of flexible ducting. Attach your inline fan on the other side of the reflector and vent the hot air directly out of your room (or tent) using more ducting. For best results, keep this path as short and straight as possible. Kinks will restrict airflow and the exhaust/ cooling system will become less efficient the longer the hot air has to travel. Also, keep enough slack in the duct work to allow for your lights to be raised and lowered.

    Air Cooled Set Up 2

    In my opinion, a much better way to set up your grow room is to use cool, filtered incoming air to remove the heat from your lights and a separate fan and filter to exhaust the air going out of your garden. While this will initially cost you more, it provides greater flexibility, a better growing environment and it’s much easier on your equipment.

    Start by attaching your in-line fan to a HEPA cleaning filter outside the room (this is your clean, cool air supply). Run flexible ducting from the fan through your grow room wall and attach it to the vent on the reflector. Attach more flexible ducting — preferably insulated — on the opposite side of your reflector and run it outside. Here’s the layout:

    Filter >>> Fan >>> Ducting >>> Wall >>> Reflector >>> Ducting >>> Outside

    Tip: You can exhaust this hot air to a garage or other area that you want to heat during winter months.

    It is always best to push cool, filtered air from outside your room (or tent) through your air-cooled hood(s). This is preferable for the following reasons:

    • All of the air being pushed into your room will be filtered and free of insects, mites, mold or mildew.

    • Pushing air into your room will create a positive air pressure which can help keep potential nasties outside.

    • Your fan will last longer because it’s not always sucking hot, damp air through it.

    Fan & Filter Exhaust System

    To get rid of the potentially smelly air inside your garden, attach a separate inline fan to a flange kit on top of your carbon filter. Make sure that the fan and filter are large enough for your growing space and vent this air outside your room using flexible ducting.

    Proper Fan Size

    It is important that you are using the right size in-line fan (CFM) for the job. To do this, measure the size of your room (tent) length x width x height and divide by 3. This will give you the minimum fan size CFM for your area.

    Example: 12 ft. x 10 ft. x 8 ft tall = 960 cubic feet / 3 = 320 CFM

    In this example 320 CFM is the minimum fan size that you will need to replace the air every 3 minutes. Once fan size is determined, match it to the appropriate sized filter.

    Happy growing!


    thanks. does anything change growing in a cold winter climate, like 25* daily?


    Eric Vinje

    Not really David, except that you won’t run into many of the heat issues most indoor gardeners experience. You can even automate your cooling set up with a temp controller that will only run your fan when your grow room temps exceed a given temperature.

    Hope this helps!



    Option 1: Set up a CAN filter inside the grow room and mount an inline fan on top. Keep in mind this will take up some space and will not vent air or heat out of the room. However, any supplemental CO2 supplied within the room will not be lost and the filter will eliminate the majority of any odor.

    Option 2: Vent air from just outside of the grow tent into the tent. Set up a CAN filter inside with an inline fan mounted on top. Duct air out of the fan through an AC reflector and out of the tent. In this situation, air is just being circulated from the room right back into the tent repeatedly.

    Option 3: Vent air into the grow room from a separate room. Have a CAN filter set up inside the grow room with an inline fan on top and vented through an AC reflector. Duct air from the other end of the reflector out into the grow room and then out into a separate room. You can vent air outside or into a basement to heat your home. *

    Option 4: Assemble a CAN filter with an inline fan outside of the grow room. Use ducting to vent the cool filtered air into the grow room and up through an AC reflector. On the other end, duct air out of the room and outside or into another room. This system will move heat out and leave more space inside the room. *

    * If you are still concerned about the smell of the air vented out, set up a separate inline fan attached to a carbon filter or another CAN filter outside of the grow room before ducting outside or into a separate room.

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