Ventilation and air circulation: fresh air for healthy plants

Air circulation is fundamental for healthy cannabis plants and mould prevention:

**Air circulation basics:**

*Why air movement is critical:*

- Strengthens stems through wind simulation

- Prevents stagnant air zones

- Reduces mould and fungus risk

- Improves CO2 distribution

- Optimises temperature distribution

*Air exchange principles:*

- Fresh air supply (passive or active)

- Used air extraction

- Internal circulation

- Temperature management

- Humidity control

**Ventilation systems:**

*Passive ventilation:*

- Utilise natural buoyancy

- Inlet at the bottom, outlet at the top

- Cost effective and quiet

- Limited control

- Suitable for small setups

*Active ventilation:*

- Axial or centrifugal fans

- Precise airflow control

- Timer and thermostat control

- Higher cost but more control

- Standard for professional setups

*Hybrid systems:*

- Passive supply air, active extract air

- Cost saving

- Good basic ventilation

- Flexible adaptation

- Ideal for medium-sized setups

**Fan size calculation:**

*Air exchange rate:*

- Minimum: 1x room volume per minute

- Optimal: 2-3x room volume per minute

- With high heat: 4-5x per minute

- Consideration of resistances

- Allow for safety surcharge

*Example calculation:*

- Room: 2m x 1m x 2m = 4m³

- Optimal: 4m³ x 3 = 12m³/min = 720m³/h

- With resistors: +30% = 936m³/h

- Fan selection accordingly

**Fan positioning:**

*Supply air fans:*

- Position at the bottom or side

- Bring in cooler outside air

- Even distribution

- Avoid direct draught on plants

- Filter for outdoor air purification

*Exhaust air fans:*

- High at the top or side

- Remove warm, humid air

- Through activated carbon filter for odour

- Highest point in the room

- Short distances to the outside

*Recirculation fans:*

- Various heights and positions

- Oscillating movement ideal

- 30-45° angle to plants

- Not direct continuous bombardment

- Smooth canopy movement

**Climate zone management:**

*Temperature stratification:*

- Warmer at the top, cooler at the bottom

- Aim for even distribution

- Identify and eliminate hotspots

- Thermometers at different heights

- Air movement for homogenisation

*Humidity zones:*

- Substrate proximity often more humid

- Canopy area critical

- Air movement reduces local humidity

- Hygrometer in various places

- Observe mould-prone areas

**Seasonal adjustments:**

*Summer ventilation:*

- Higher air change rates

- Use night air for cooling

- Additional recirculation fans

- Possibly integrate air conditioning

- Maximise heat dissipation

*Winter ventilation:*

- Reduced air exchange

- Partially recirculate warm exhaust air

- Frost protection for supply pipes

- Heating integration

- Optimise energy efficiency

**Controller and automation:**

*Temperature-controlled:*

- Switch on fans in the event of overheating

- Step-by-step speed control

- Hysteresis function

- Day/night profiles

- Alarm functions

*Humidity