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Contributor
BUILDING PHARMA-GRADE AHUs : BEST PRACTICES FOR DESIGN , MANUFACTURING AND INSTALLATION
By Ryan Rennie , from the Spada-Rennie Group
Air Handling Units ( AHUs ) are the backbone of pharmaceutical HVAC systems , playing a critical role in maintaining precise temperature , humidity , room pressure and cleanliness levels .
The pharmaceutical industry has stringent regulatory requirements , including Good Manufacturing Practices ( GMP ), ISO 14644 , and other regional guidelines , making the design and manufacturing of AHUs more complex than in other industries . This article outlines best practices for designing , manufacturing , and installing pharma-grade AHUs to ensure compliance , efficiency , and long-term reliability .
DESIGN CONSIDERATIONS FOR PHARMA AHUS 1 . Material selection and construction Pharmaceutical AHUs must be built from materials that resist corrosion , microbial growth and contamination . The most commonly used materials include :
• Stainless steel ( SS 304 / 316L ) – Ideal for internal surfaces in high-contamination areas
• Chromadek – Lightweight and resistant to chemical exposure
• Double-skinned panels with insulation – Provides thermal efficiency and minimises condensation risk
AHUs should be designed with smooth internal surfaces to prevent dust accumulation and microbial growth . Welded joints and minimal fasteners inside the unit help maintain a contaminationfree environment .
2 . Filtration strategy Air filtration is a critical component of pharma-grade AHUs . A multistage filtration approach is required to meet cleanroom standards :
• Primary filters ( G4 / MERV 8 ) – Captures larger particulates to extend the life of fine filters
• Secondary filters ( F7-MERV 13 / F9-MERV 15 ) – Removes smaller particles before air enters critical areas
• HEPA filters ( H13 / H14 ) – Essential for cleanrooms , removing 99.97 % of particles ≥0.3 microns
The filter selection depends on the cleanroom classification and risk assessment of the pharmaceutical process .
3 . Airflow control and pressurisation Maintaining the correct air balance and pressure differentials is crucial to preventing cross-contamination . AHUs should be designed to :
• Ensure positive pressurisation in clean areas
• Maintain unidirectional airflow in sterile environments
• Use Variable Air Volume ( VAV ) controls to optimise energy use
4 . Energy efficiency measures Pharma facilities operate 24 / 7 , making energy efficiency a key factor in AHU design . Best practices include :
• Heat recovery wheels and run-around coils – Reduce heating and cooling loads by reclaiming energy
• EC fans with Variable Frequency Drives ( VFDs ) – Improve efficiency by adjusting fan speed to real-time demand
• Intelligent control systems – Optimise airflow and temperature based on occupancy and environmental conditions
MANUFACTURING BEST PRACTICES 1 . Precision fabrication and assembly AHUs must be manufactured with high precision to ensure compliance with pharmaceutical regulations . Best practices include :
• Automated welding and bending to minimise human error
• Modular construction for ease of assembly and maintenance
• Rigorous surface finishing to eliminate microbial growth risks
2 . Factory Acceptance Testing ( FAT ) Before an AHU leaves the manufacturing
Ryan Rennie , from the Spada-Rennie Group .
Supplied by Ryan Rennie
www . refrigerationandaircon . co . za RACA Journal I April 2025 43