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When it comes to indoor gardening and hydroponics, most growers are well-versed in using carbon filters on their outlet ducts to manage odours. But what about the inlet filter?
In this blog we go over why inlet filters are just as essential—and often overlooked. Whether you’re running a commercial setup or a hobby grow room, understanding how to control what comes in is just as important as what goes out.
An inlet filter is a simple mesh or fabric cover that goes over the air intake duct of your grow room. Unlike carbon filters for smell control, inlet filters serve to block pests, spores, and virus vectors from entering your controlled environment.
Key benefits include:
Many pests simply can’t fly high, so placing your inlet high off the ground (e.g. second floor or roof level) can drastically reduce insect entry.
With a fine mesh filter—something as simple as an old pair of tights or pantyhose—you can block:
💡 Pro Tip: Use a mesh tight enough to block pests, but not so dense it restricts airflow. Avoid fishnet-style tights, and ensure both the interior and exterior ends of the duct are covered to keep pests out during maintenance.
While inlet filters are great for insects and some viral vectors, they won’t stop everything. Most filters won’t block:
Blocking particles under 50 microns requires commercial-grade HEPA filters, which need powerful fans and can be noisy and energy-intensive.
An unusual but effective method for managing fungus gnats:
“We placed a pot of decomposing grow media above an insect electrocution unit—it attracts gnats like a charm. It’s not health and safety approved, but it works!”
That said, inlet filters remain the safer and more scalable option for most growers.
Aphids and thrips are virus vectors. They don’t carry diseases themselves but transmit them between plants. By blocking these vectors, you’re also protecting your crops from virus outbreaks.
Keep in mind:
So proper filtering + good sanitation practices = maximum protection.
Grow room doors left open are open invitations for:
Keep your environment sealed and monitored at all times.
Inlet filters are an often forgotten, but critical component of hydroponic hygiene. They’re cheap, easy to DIY, and provide essential defence against pests and diseases. Whether you’re protecting your tomato plants or growing something more specialized, a mesh filter might just save your crop.
Have a favourite filter hack or product? Drop us a message!
Article by Dr Russell Sharp
If you would like to keep up to date with subjects just like this, you can listen to both our podcasts! Links can be found bellow:
Hydroponics Daily Podcast: Illustration of an inlet air filter with surrounding bugs, sparkles, and bold text reading “Why You Need an Inlet Filter in Hydroponics” on a bright yellow and blue background
Cereal Killers Podcast: https://t.co/eSEbBkTVHl