Ventilation and air circulation: optimising the fresh air system

Optimal ventilation is critical for healthy cannabis plants and mould prevention:

**Why ventilation is important:**

- CO2 replenishment for photosynthesis

- Removal of excess moisture

- Temperature regulation

- Prevent mould and fungi

- Reduce odours

- Strengthen plants through light movement

**Exhaust air system**

Remove warm, humid air from the grow room.

*Components:*

- Exhaust air fan (main component)

- Activated carbon filter (odour removal)

- Aluminium hose for air transport

- Silencer (optional, for noise reduction)

*Dimensioning:*

- Room volume x 40-60 = required m³/h

- Example: 1m x 1m x 2m = 2m³ → 80-120 m³/h fan

**Supply air system**

Bring fresh, cool air into the grow room.

*Passive supply air:*

- Holes/slots at the bottom of the tent

- Area = 1.5x exhaust air cross-section

- Inexpensive, but less control

*Active supply air:*

- Separate supply air fan

- Better control over airflow

- Higher costs, more energy consumption

**Air circulation in the room**

Fans for moving the air between the plants.

*Clip fans:*

- 1-2 small fans per m²

- Do not point directly at plants

- Continuous operation for constant movement

*Oscillating fans:*

- Swivelling movement for even distribution

- Particularly effective with dense vegetation

**Monitor climate parameters:**

- Temperature: 20-26°C (growth), 18-24°C (flowering)

- Humidity: 40-60% (growth), 40-50% (flowering)

- Observe VPD (Vapour Pressure Deficit)

**Avoid common mistakes:**

- Exhaust air too weak = waterlogging, mould

- Excessive exhaust air = negative pressure, stressed growth

- No circulation = hot spots, uneven growth

- Not changing filters in time = odour problems