AHU URS in Pharmaceuticals serves as the foundation for selecting an HVAC system that consistently maintains cleanroom conditions in pharmaceutical manufacturing. It clearly defines the operational, design, regulatory, and performance requirements before purchasing or manufacturing an AHU.
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Objective for AHU URS :
The primary objective of an Air Handling Unit (AHU) User Requirement Specification (URS) is to clearly define the technical, operational, and regulatory requirements of the AHU before its design, procurement, or installation. A well-prepared URS helps equipment manufacturers and suppliers understand the pharmaceutical company’s expectations regarding system performance, construction, capacity, air filtration, environmental control, and compliance with current Good Manufacturing Practices (cGMP).
In addition, the AHU URS serves as a reference document for obtaining accurate technical proposals and commercial quotations from suppliers. It outlines the required design features, qualification support, documentation, testing, and performance criteria to ensure the selected HVAC system is capable of maintaining the specified cleanroom conditions. By establishing these requirements at the initial stage, the URS minimizes design changes, simplifies vendor selection, and ensures that the Air Handling Unit consistently meets operational needs, regulatory requirements, and product quality standards throughout its lifecycle.
Approval of Documents:
Prepared by:-
| Name | Designation/Department | Signature | Date |
| Executive/ QA |
Reviewed by:-
| Name | Designation/Department | Signature | Date |
| Manager/Production | |||
| Manager/Engineering |
Approved by:-
| Name | Designation/Department | Signature | Date |
| Manager/QA |
Scope for AHU URS in industry
The scope of an Air Handling Unit (AHU) User Requirement Specification (URS) is to define the functional, technical, operational, and regulatory requirements for the Air Handling Unit to be installed in a pharmaceutical facility. It serves as a comprehensive guideline for the design, procurement, manufacturing, installation, testing, qualification, and commissioning of the AHU to ensure it meets the environmental control needs of the intended application.
Location of equipment:
Machine will be installed in service area in your company.
Guideline Reference
ISO 14644-1. Cleanrooms and Associated Controlled Environments
System/equipment/Instruments details for AHU URS
| Parameter | Description |
|---|---|
| Equipment Name | Air Handling Unit (AHU) |
| Model/Type | cGMP-compliant model, customized as per the application and cleanroom classification |
| Capacity | Designed according to the required airflow (CFM), air changes per hour (ACH), and room volume |
| Application | Temperature, humidity, air filtration, and pressure control in pharmaceutical manufacturing areas |
| Compliance | Designed to meet applicable cGMP, WHO, EU GMP, and other regulatory requirements, where applicable |
Scope of Supply:
| Parameter | Requirement |
|---|---|
| Type of Device | Air Handling Unit (AHU) |
| Regulatory Compliance | Designed in accordance with current Good Manufacturing Practices (cGMP) and applicable WHO and EMA guidelines. |
| Machine Safety Standards | The AHU should comply with ISO 13852:1996 and ISO 13853:1996 to ensure safe operating distances and protect personnel from moving machine parts. |
| Design Features | cGMP-compliant construction with smooth internal surfaces, easy cleaning, operator safety, simple operation, and low-maintenance design. The system should include a Variable Frequency Drive (VFD) for efficient motor speed control. |
| Operation & Maintenance Documents | Operator manual, installation manual, maintenance manual, troubleshooting guide, safety instructions, assembly drawings, and user manuals for all supplied components. |
| Electrical Documentation | Single-line electrical diagram, circuit diagrams, cable schedule, and electrical equipment layout drawings. |
| Qualification Support | Vendor should provide Design Qualification (DQ), Factory Acceptance Test (FAT), Site Acceptance Test (SAT), Installation Qualification (IQ), and Operational Qualification (OQ) protocols and reports. Technical support for Performance Qualification (PQ) should also be included. |
| Training | Comprehensive operational training for production personnel and preventive maintenance training for engineering and maintenance staff. |
| Testing & Certification | FAT test reports, material certificates (MOC), calibration certificates for measuring instruments, and test certificates for purchased components should be supplied with the equipment. |
Brief system description:
Air handling unit is sometimes abbreviated as “AHU.” As the name implies, an air handling unit is a piece of equipment that handles air. Its internal structure is very simple. The air handling unit (AHU) is the heart of central air conditioning. It collects outside air and room air, removes dust and other particles from the collected air, adjusts the temperature and humidity and then supplies comfortable and refreshing air-conditioned air into the rooms through ducts.
Air handling unit is a huge indoor unit of commercial air conditioning equipment. This massive “indoor unit” is installed on a rooftop or along an external building wall. It produces cool/warm air and sends it to the rooms for cooling/heating. Unlike ordinary commercial air conditioners, air handling units are usually made to order for individual buildings. Furthermore, air handling units can be customized by internally mounting a filter, humidifier and other devices for the control of temperature, humidity, air flow and air cleanliness.
The basic construction of the machine consists for AHU URS :
| Component | Material / Specification |
|---|---|
| AHU Panel | Galvanized Iron (GI) double-skin panel with suitable insulation |
| Process Blower | Mild Steel (MS) construction or equivalent material suitable for the application |
| Air Ducting | Galvanized Iron (GI) ducting with leak-proof joints |
| Dampers | Aluminium dampers with corrosion-resistant finish |
| Condensate Collection Tray | Stainless Steel SS 304 with proper slope for complete drainage |
| Control Panel | Powder-coated Galvanized Iron (GI) panel with pre-wired electrical components |
| Air Contact Surfaces | Smooth, non-porous surfaces free from welding burrs, sharp edges, and crevices. All joints should be sealed with suitable silicone sealant to prevent dust accumulation and facilitate easy cleaning. |
The Drive:
The machine is equipped with frequency controlled drive. A large torque can be achieved even at low speed and because of its high regulating speed. The is centrally driven by an electric motor.
Key Features of the AHU Drive System in AHU URS
- Variable Frequency Drive (VFD) for precise fan speed control.
- High torque available even at low operating speeds.
- Energy-efficient operation with reduced power consumption.
- Centrally driven electric motor for smooth and reliable performance.
- Stable airflow control to maintain temperature, humidity, and pressure.
- Reduced mechanical wear, resulting in lower maintenance requirements.
- Suitable for continuous 24/7 operation in pharmaceutical facilities.
Grill/ Air Intake Screen
On the front of every AHU is a grill (or Air Intake Screen) to prevent large, unwanted objects from entering the system and potentially causing damage or a blockage.
Damper
The first internal component of any AHU is the damper. This is multiple sheets of rotating metal that are used to adjust the volume of air entering the AHU. They can open and close fully and also open partially. As well as controlling the volume of air, dampers are important when it comes to preventing the spread of fire, closing to act as a fireproof break two sides.
Filters
Having passed through the frost protection coil, the air then passes through a filter. This removes any small dust and dirt particles that, if allowed to enter the system further, would damage the components and would also result in people breathing in contaminated air. There are two types of filter – panel filter and bag filter
Mixing Box
A mixing box helps increase the energy efficiency of an AHU by recirculating returning air from the ductwork (from the zones/rooms) and mixing it with fresh air being introduced from outside. The heat from the returning air is used to heat the outside air, thereby reducing the energy output required from the AHU itself.
Cooling & Heating Coils
These set the temperature that leaves the AHU. A thermostat is used to ascertain the temperature of the air in the AHU. If the air is deemed too hot, the heating coil will be activated and vice versa. This desired temperature is known as the Set Point.
Supply Fan
The fan circulates the air from the AHU, into the ductwork, along to the various zones. It pulls the air into itself and then propels it out. The speed at which the air leaves the fan can be controlled. Historically these were centrifugal fans but for increased efficiency they are now EC (Electronically Communicated) fans .Fans has a pressure sensor to ensure they are running and functioning correctly.
Secondary Filter
A secondary filter further filters the air in the AHU before it leaves and continues its journey through the ductwork.
Dehumidifier
Depending on the geographic location and requirements of the building, some AHUs also have a humidifier (and humidity sensor). The sensor measures the level of moisture in the air, should the level need to be controlled. A humidifier is usually one of the last components in an AHU and if deemed unnecessary, they may be turned off to increase efficiency.
Control Panel
Every AHU will have a control panel, featuring individual switches and run and trip indicators for the fan and heater. There are three different types of control panel: single stage control panel, 3 step control panel and 6 step control panel, referring to the number of steps of heater control.
Electrical chamber and mechanical chamber:
All mechanical components such as gears, motors, and moving belts, as well as electrical components such as wiring, switches, and MCBs, are installed in this segment.
Technical Specification for AHU URS:
| Parameter | Specification |
|---|---|
| Model / Type | cGMP-compliant model suitable for pharmaceutical applications |
| Capacity | As per process and room requirements |
| Operating Speed | Variable speed as required using a Variable Frequency Drive (VFD) |
| Overall Dimensions | Customized according to installation space |
| Variable Frequency Drive (VFD) | Selected according to motor rating for energy-efficient airflow control |
| AHU Construction | Double-skin insulated panels with CRC powder-coated outer surface |
| Airflow Capacity (CFM) | Designed based on cleanroom airflow calculations |
| Blower | Sized according to the required airflow (CFM) |
| Air Changes Per Hour (ACH) | Minimum 20 air changes per hour for ISO 8 (Grade D) cleanrooms at rest |
| Particulate Classification | Should comply with ISO 8 / Grade D cleanroom requirements |
| Microbial Limits | Should meet the specified microbiological limits for the classified area |
| Recovery Time | Cleanroom recovery should be achieved within 15 minutes |
| Temperature & RH Recovery | Temperature and relative humidity should return to the specified range within 30 minutes |
| Airflow Pattern | Uniform airflow with proper supply and return air distribution. Air should flow from higher-pressure areas to lower-pressure areas. |
| Fresh Air Requirement | Minimum 10% fresh air or as per HVAC design |
| Operating Mode | Auto and Manual operation with VFD compatibility |
| System Performance | Designed for continuous operation 24 hours a day, 7 days a week |
| Equipment Identification | Equipment name, model, serial number, capacity, manufacturer, and year of manufacture should be clearly displayed |
Safety Features:
| Critical Variables | Acceptance Criteria | Reference |
| MCB | MCB is provided so that when there is an overload in current or any short circuit then the MCB trips. | Safety Requirement |
| Mechanical Guard | Mechanical guard for all rotating parts. | Safety Requirement |
| Joints | Welding of joints without any welding burrs. | Safety Requirement |
| Metal Parts | All the metal parts should be properly grounded without any sharp Edges. | Safety Requirement |
| Leveling and Balancing | Equipment should be properly balanced & leveled. | Safety Requirement |
| Installation | All the Installation must be in accordance with the cGMP. | Safety Requirement |
| View lamp and view window | FLP / NFLP view lamp should be provided in blower section with view glass on panel. | Safety Requirement |
| Alarm system | Alarm should be provided. | Safety Requirement |
| Electrical Wiring And Earthing | Electrical wiring should be as per approved drawings. Double external Earthing to control machine (panel and motors) and operator should be provided. | Safety Requirement |
| Noise Level | Below 80 db. | Safety Requirement |
| Emergency/Safety Switch | Provided easy access position | Safety Requirement |
Air Filtration System in AHU URS
An efficient filtration system is essential to remove airborne particles and maintain cleanroom cleanliness.
| Filter Stage | Typical Specification |
|---|---|
| Fresh Air Filter | 90% efficiency (10 µm) |
| Pre-Filter | EU4, approximately 90% efficiency (10 µm) |
| Fine Filter | EU9, approximately 99% efficiency (5 µm) |
| HEPA Filter | EU13, 99.997% efficiency at 0.3 µm |
| HEPA Integrity Testing | PAO testing ports should be provided, and on-site leak testing should be performed after installation |
| Access Doors | Access ports should be provided for HEPA filter integrity testing and maintenance |
Spare parts / Change parts
Vendor should provide Preventive Maintenance SOP, List of recommended critical spare parts with code no. considering 2 years of satisfactory working of machine. After Sale Service/ AMC for the machine should be provided after warranty period. Vendor should provide all spares required for 2 years of use at the time of shipment.
Additional Design Features
To ensure long-term performance and regulatory compliance, a pharmaceutical AHU should also include:
- Differential pressure monitoring across each filter stage.
- Low-leakage aerofoil dampers with positive locking arrangements.
- Flameproof heaters where specified.
- Desiccant wheel for humidity control, if required by the process.
- Proper sealing of all duct joints using gaskets and sealants.
- Continuous monitoring of airflow, temperature, humidity, and pressure.
- Easy access for inspection, maintenance, cleaning, and qualification activities.