Frenquently Asked Questions
As a general rule, you should aim to exchange the air in your grow space every 1–3 minutes. To calculate the required fan capacity, multiply your room volume (length × width × height in metres) by 20–60 to get the minimum m³/h rating. For example, a 1.2m × 1.2m × 2m tent (2.88m³) needs a fan rated at least 58–173 m³/h.
CFM (cubic feet per minute) and m³/h (cubic metres per hour) are both units of airflow. To convert CFM to m³/h, multiply by 1.699. So a 200 CFM fan equals approximately 340 m³/h. Most UK and EU fans are rated in m³/h, while US products often use CFM.
Your carbon filter should be rated at the same or higher m³/h than your fan. Using an undersized filter will reduce its effectiveness and shorten its lifespan. Mammoth Carbon Filters are sized to match common fan ratings — check the product specifications for the recommended fan pairing.
Most carbon filters last 12–18 months under normal use, but this depends on humidity levels, air quality, and how continuously the fan runs. High humidity (above 70% RH) can saturate the activated carbon faster. Running your fan at a lower speed with a fan controller can extend filter life significantly.
Static pressure (measured in Pa or mmH₂O) matters when air has to pass through ducting, bends, or a carbon filter — all of which create resistance. For most grow tent setups with a carbon filter and 1–2m of ducting, look for a fan with at least 150–250 Pa of static pressure to maintain effective airflow.