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Inside an Advanced Air Handling Unit (AHU): Complete Air Treatment Process Explained

 Inside an Advanced Air Handling Unit (AHU):

Complete Air Treatment Process Explained


Designing a high-performance HVAC system-especially for critical environments like pharmaceuticals, cleanrooms, or healthcare-requires precise control over air quality, temperature, and humidity.


Here's a step-by-step breakdown of how air is processed inside a modern Air Handling Unit (AHU):


1. Return & Fresh Air Intake

The process begins with a combination of Return Air (RA) from the space and Outdoor Air (OA). These streams enter through the intake plenum, where the return fan helps maintain proper airflow balance.


2. Mixing Section

Fresh and return air are mixed in controlled proportions to maintain indoor air quality while optimizing energy efficiency.


3. Pre-Filtration Stage

Air passes through pre-filters and intermediate filters, removing dust and larger particles-protecting downstream components and improving system life.


4. Energy Recovery Coil (Optional)

An energy recovery system transfers heat between exhaust and incoming air streams, reducing overall energy consumption.


5. Heating Coil Section

If required, air is preheated to maintain desired conditions, especially in colder climates.


6. Humidification (Optional)

A humidifier adds moisture to the air to maintain required relative humidity levels-critical for product quality and comfort.


7. Cooling Coil Section

Air is cooled and dehumidified as it passes through the cooling coil, removing excess heat and moisture.


8. Dehumidifier Unit

For applications requiring tight humidity control, a dedicated dehumidifier ensures precise moisture removal beyond standard cooling.


9. Re-Cooling & Reheating

Air may undergo re-cooling and reheating to fine-tune temperature and humidity-this is essential for achieving exact environmental conditions.


10. Supply Fan Section

The conditioned air is then pushed by the supply fan toward the final stage.


11. Final Filtration

High-efficiency filters (HEPA/ULPA, if required) ensure the air meets strict cleanliness standards before entering the controlled space.


12. Supply Air (SA)

Finally, clean, conditioned air is delivered to the room, maintaining the desired environment.



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