An inline extractor fan pulls warm, humid air out of the grow tent and draws it through the carbon filter. The rule of thumb: tent volume × 60 × 1.3–1.5. A 120x120x200 tent needs 225–260 m³/h of real airflow, which means a 125 mm fan rated at 300–400 m³/h. Here you will find PrimaKlima, S&P and Can-Fan from 125 to 315 mm.
The tent volume (width × depth × height, in m³) multiplied by 60 gives the airflow for one complete air change per minute. The factor of 1.3–1.5 makes up for the carbon filter, ducting and bends, which all slow the air down. Rated airflow is measured with no resistance, so pick a fan with headroom and turn its speed down.
| Grow tent (cm) | Volume | Calculated airflow | Typical diameter |
|---|---|---|---|
| 60x60x160 | 0.6 m³ | 45–52 m³/h | 100 mm |
| 80x80x160 | 1.0 m³ | 80–92 m³/h | 100 mm |
| 100x100x200 | 2.0 m³ | 156–180 m³/h | 100–125 mm |
| 120x120x200 | 2.9 m³ | 225–260 m³/h | 125 mm |
| 150x150x200 | 4.5 m³ | 350–405 m³/h | 150–160 mm |
| 240x120x200 | 5.8 m³ | 450–520 m³/h | 160–200 mm |
With HPS lamps or in a warm room, aim for the top of the range; grow rooms need models from 200 mm upwards. Fans in this category start at 125 mm: for tents up to 80x80 there are the 100 mm AC Infinity kits, or a 125 mm EC fan run at low speed.
If you prefer fan, filter and controller already matched, see the ventilation kits; the right filter for each diameter is among the carbon filters.
All prices are in Swiss francs including Swiss VAT. We ship throughout Switzerland with Swiss Post; bulky parcels go by courier. To choose the right diameter, email our support team or call +41 79 359 67 58: Gro.w.LaB also gives advice in the shop in Quartino, by appointment.
Multiply the tent volume in m³ by 60 and then by 1.3–1.5. For a 120x120x200 tent that gives 225–260 m³/h of real airflow, so a 125 mm fan rated at 300–400 m³/h.
With a carbon filter and ducting you need a fan that holds its airflow against resistance, which is why grow tents use centrifugal or mixed-flow inline fans. A simple axial fan loses a lot of airflow as soon as a filter is attached.
Yes, if the fan runs for long hours: it uses less power, adjusts smoothly and is quieter at low speed than an AC fan with a controller.
