A Brief Guide to Extraction Systems

When it comes to indoor growing, there are three main areas to focus on: lighting, extraction and grow systems. In this blog, we’re going to talk about extraction systems, so that you can understand why you need one and how they work.

What Does a Typical Extraction System Consist Of?

The main components required are a duct fan, a carbon filter and ducting.


Your extraction system starts with a carbon filter – a mesh cylinder filled with activated carbon, and lined with an external layer of fabric.


Next comes the duct fan which is usually (but not always) directly attached to your filter.


The fan sucks air through the filter, directing it out of the room via the ducting. Duct fans come with powerful motors that allow them to move large volumes of air from your grow space.


So Why Do I Need an Extraction System?

Environmental conditions have a huge impact on the success of your indoor garden. That’s because these conditions directly impact photosynthesis – the main driver of plant growth. You can find out more about the science of photosynthesis by checking out this blog post. In short, your extraction system optimises photosynthesis rates by regulating temperature levels, moisture levels, and the replenishment of CO2. As an added bonus, your extraction system is also used for odour control.

Temperature and Moisture

Grow room heat and humidity levels decide how quickly plants lose moisture, which impacts leaf stomata. If heat and humidity levels are less than favourable, the stomata close up, which slows down photosynthesis. The more technical people out there will want to look into vapour pressure deficit, which gives you the most accurate window into grow room conditions, but to keep it simple, aim for temperatures of around 25 degrees celsius during daylight hours and 18 degrees during dark periods. Aim for humidity levels of at least 60% during the vegetative growth stages and around 50% during bloom. By keeping conditions within the right ranges, leaf stomata stay open, optimising photosynthesis rates.

When your extraction system sucks air from the grow room, it takes excess heat and moisture with it, pulling in cool, fresh air from outside. That’s why it is your main weapon in tackling environmental problems. Fan speed controllers take this a step further by automatically ramping up output levels when conditions get out of ideal ranges, dropping levels back down when it’s safe to do so.

By tackling high temperature levels and excess moisture, you’ll also reduce the likelihood of encountering powdery mildew and botrytis (rot) – common fungal problems that can devastate entire crops and are best avoided!

Carbon Dioxide

Carbon dioxide (CO2) is required by plants for the process of photosynthesis. CO2 is absorbed through open leaf stomata, and plants use light energy from your grow lamp (or the sun) to separate that CO2 into carbon and oxygen. The carbon is used to manufacture sugars that form the plant’s structure and the oxygen is discarded as a bi-product. Your extraction system sucks CO2 depleted air out of the room, bringing in fresh, CO2-rich air as a replacement.

Odour Control

Many plants give out pungent odours! This is something that you’ll most likely want to stay on top of, and the carbon filter in your extraction system is there to deal with this issue. Air from the grow space is sucked through the filter before it exits the room. As it passes through the filter, it’s forced to travel through a layer of carbon, which has a cleaning effect, removing impurities. Any air that gets dumped outside is then completely smell free. Note that carbon filters have a finite life span, so they’ll need to be replaced at least every two years (some models sooner).

Don’t forget that if you have any other questions, you can give us a call or come and see us in-store.

Products mentioned in the article

Hyper fan group image
Choose the size of your duct fan:
6-inch (150mm) – 560m3/hr

£174.95 £174.95
766180 10 inch
Choose your fan size:
6" (150mm) 796m3 p/h

£444.95 £444.95
110309 100mm 4 inch rvk   rhino pro 175m3 hr extraction kit v2
Choose your size:
4" (100mm) 184m3/hr

£119.95 £119.95