Air Handling Units · Heating · Ventilation · Cooling · Humidification · Dehumidification
AHU, HVAC
HVAC is the central unit to which AHU is connected and is a key technology for pharmaceutical environmental control.
The Heating, Ventilating and Air Conditioning system uses the principles of fluid mechanics, thermodynamics and heat transfer. HVAC is used to condition the atmosphere in facilities and barrier systems like isolators.
HVAC systems play a crucial role in pharmaceutical engineering and manufacturing because they have a direct impact on the production environment. Optimized HVAC units can help pharmaceutical companies manage airborne contaminants, pass inspections, and remain cGMP-compliant.
HVAC, AHU design considerations
- An AHU consists of fans, coils and filters residing within an insulated metal box. A pharmaceutical grade AHU has a double-walled exterior with insulation sandwiched between the two walls, so the interior can be cleaned and the airflow is not contaminated from the insulation layer.
- In a pharmaceutical application, Air Handling Units must be air-tight and epoxy coated to prevent outside contamination.
- A pharmaceutical grade AHU should have good access doors, view ports, electrical convenience outlets and interior lighting for maintenance.
- The casings should be tightly sealed and designed for pressures higher than commercial applications.
- All sealants and lubricants exposed to the airstream should be food grade to minimize the chance of air contamination.
- Cooling coils typically circulate chilled water or propylene glycol solutions instead of direct expansion refrigerant, as this is more reliable and better suited to maintaining tight temperature ranges.
- Cooling coils need a drain pan to receive condensate. A stainless steel media eliminator plate may need to be installed downstream of the cooling coil to remove fine mist and prevent excess water from entering the system.
- The fan must be balanced and have a shaft seal near the bearings.
- A separate Make-up Air Handling Unit (MAHU) provides outside air to supply the AHU units. Make-up air typically provides 10–20% of the recirculated air.
- A Process Air Handler (PAHU) provides pre-conditioned air from the Make-up Air Handler directly to the aseptic core, for example Grade A air supply.
- Fresh air intake dampers should be mounted on the suction side of the AHU fan.
- Pharmaceutical air handling units should be located in a separate equipment space or floor to allow access and maintenance without disturbing cleanroom areas.
- Independent AHUs should be used for different manufacturing areas, such as tableting, compounding and aseptic filling, to prevent cross-contamination.
- The AHU should be placed as close as possible to the area served to reduce the length of ductwork required.
- Air returns are located at the bottom of the cleanroom wall.
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