AHU for Cleanrooms

What Is an AHU for Cleanrooms?

An Air Handling Unit (AHU) for cleanrooms is a specialized air-conditioning and ventilation unit designed to supply conditioned and filtered air to controlled environments.

Depending on the application, a cleanroom AHU can include:

• Fresh-air section
• Return-air section
• Pre-filters
• Fine filters
• Cooling coil
• Heating/reheat section
• Dehumidification
• Humidification where required
• Supply fan
• VFD
• HEPA filtration
• Differential-pressure monitoring
• Temperature sensors
• Humidity sensors
• Control dampers
• Access sections
• BMS integration

The final configuration depends on the cleanroom classification, process requirements, room size, occupancy, heat load, contamination-control strategy and applicable project standards.

Why Is AHU Important for Cleanrooms?

A conventional commercial HVAC system is generally not sufficient for applications requiring tightly controlled air cleanliness.

Cleanroom HVAC systems need to consider several parameters simultaneously:

• Air cleanliness
• Airflow quantity
• Airflow pattern
• Air changes
• Temperature
• Relative humidity
• Pressure differential
• Filtration
• Fresh air
• Return air
• Exhaust air
• Energy consumption
• Monitoring and controls

The AHU therefore becomes one of the key components of the overall cleanroom environmental-control system.

Cleanroom HVAC Design Requirements

Cleanroom HVAC design should begin with the intended use of the room.

Different cleanrooms may have different requirements depending on the process and cleanliness classification.

Important design considerations include:

1. Cleanroom Classification

The required cleanliness level should be established before determining the HVAC design.

The design may consider applicable cleanroom classification standards and the project’s specific requirements.

2. Airflow

Airflow must be sufficient to achieve the required environmental conditions and contamination-control strategy.

3. Filtration

The filtration arrangement may include multiple stages, such as pre-filtration, fine filtration and HEPA filtration.

4. Temperature

The HVAC system should maintain the required temperature range for the process and occupants.

5. Humidity

Humidity control may be particularly important for pharmaceutical, electronics, food, laboratory and other sensitive applications.

6. Pressure

Pressure differences between rooms can be used to control airflow direction and support contamination-control strategies.

Cleanroom Airflow Design

Airflow is one of the most important elements of cleanroom HVAC design.

A cleanroom system should consider:

• Supply-air quantity
• Return-air quantity
• Fresh-air quantity
• Exhaust-air quantity
• Air changes
• Air velocity
• Airflow pattern
• Room pressure
• Heat load
• Filtration
• Room volume

A simplified cleanroom airflow arrangement can be represented as:

AHU → Filtration → Supply Duct → HEPA Filter → Cleanroom → Return Air → AHU

The actual configuration depends on the cleanroom application.

Air Changes Per Hour (ACH)

Air Changes Per Hour (ACH) indicates how many room volumes of air are supplied or removed during one hour.

The required ACH should not be selected using a universal value for every cleanroom.

It depends on factors such as:

• Cleanroom classification
• Room volume
• Occupancy
• Process
• Equipment
• Contamination generation
• Required cleanliness
• Airflow pattern
• Heat load

A cleanroom HVAC engineer should calculate the required airflow based on the project design criteria.

HEPA Filtration for Cleanrooms

HEPA filtration is widely used in cleanroom applications where high-efficiency particulate filtration is required.

HEPA filters may be installed:

• Inside the AHU
• In terminal filter housings
• At cleanroom ceiling terminals
• In dedicated filtration units

Important HEPA design considerations include:

• Filter efficiency
• Airflow
• Face velocity
• Pressure drop
• Filter housing
• Sealing
• Gasket condition
• Leakage control
• Maintenance access
• Differential-pressure monitoring
• Integrity testing where required

Simply installing a HEPA filter does not by itself guarantee the required cleanroom performance. The complete airflow and filtration system must be properly designed, installed and tested.

Cleanroom Pressure Control

Pressure control is an important part of cleanroom HVAC design.

A cleanroom can be designed with a pressure relationship relative to adjacent areas depending on the process and contamination-control requirements.

Positive Pressure Cleanroom

A positive-pressure cleanroom is maintained at a higher pressure than adjacent areas so that air tends to move outward when openings permit.

This approach may be used where protection of the cleanroom from surrounding contamination is required.

Negative Pressure Room

A negative-pressure room is maintained below the pressure of adjacent spaces so that air tends to flow into the room.

This can be used where containment of contaminants is required.

Pressure Cascade

Multiple rooms can be arranged in a pressure cascade to control the direction of airflow between different zones.

Cleanroom Temperature & Humidity Control

Temperature and humidity control are important for many cleanroom applications.

The AHU design may incorporate:

• Cooling coils
• Heating coils
• Reheat systems
• Dehumidification
• Humidification
• Temperature sensors
• Relative-humidity sensors
• Automatic control valves
• VFD-controlled fans

The required temperature and humidity range should be determined by the process and project specifications.

Cleanroom AHU Filtration Stages

A cleanroom AHU may use several filtration stages.

A typical arrangement can be:

Fresh Air → Pre-Filter → Fine Filter → Cooling Coil → Fan → HEPA Filter → Cleanroom

Depending on the design, the HEPA filter may instead be located at the terminal supply point.

Pre-Filter

Pre-filters help protect downstream components and higher-efficiency filters.

Fine Filter

Fine filtration provides additional particulate removal before air reaches the final filtration stage.

HEPA Filter

HEPA filtration provides high-efficiency particulate removal for applications requiring this level of filtration.

Cleanroom AHU Construction

Cleanroom AHUs may require specialized construction depending on the application.

Potential design features include:

• Double-skin panels
• Smooth internal surfaces
• Thermal insulation
• Low-leakage construction
• Suitable drain-pan design
• Sloped condensate drainage
• Access doors
• Filter sections
• Inspection sections
• Corrosion-resistant components where required
• Suitable internal finishes
• Maintenance access

The appropriate construction should be selected according to the cleanroom application and project specification.

Cleanroom HVAC Duct Design

Ductwork plays a major role in delivering filtered air to cleanrooms.

The duct design should consider:

• Air velocity
• Static pressure
• Pressure losses
• Leakage
• Insulation
• Cleanability
• Access
• Air balancing
• Supply-air distribution
• Return-air arrangement
• Exhaust requirements

Proper duct sizing also helps the HVAC system operate efficiently while maintaining the required airflow.

Cleanroom Air Distribution

Air distribution should be designed according to the room’s cleanliness and process requirements.

Common arrangements may include:

• Ceiling supply
• HEPA terminal supply
• Low-level return
• High-level return
• Wall return
• Perimeter return
• Unidirectional airflow arrangements where required

The supply and return locations should be coordinated to establish the intended airflow pattern.

Cleanroom AHU Controls & BMS

Modern cleanroom HVAC systems can incorporate automation and monitoring.

The control system can monitor:

• Supply-air temperature
• Return-air temperature
• Room temperature
• Relative humidity
• Room pressure
• Filter differential pressure
• Fan status
• VFD speed
• Damper position
• Valve position
• AHU status
• Alarm conditions

Where required, the system can be integrated with a Building Management System (BMS).

Testing & Commissioning of Cleanroom HVAC

A cleanroom HVAC system should be properly tested and commissioned after installation.

Depending on project requirements, testing can include:

• AHU performance testing
• Airflow measurement
• Air balancing
• Room pressure testing
• Temperature measurement
• Humidity measurement
• Filter differential-pressure checks
• HEPA filter integrity testing where required
• Airflow visualization where specified
• Control-system testing
• Alarm verification

Testing requirements should be established according to the cleanroom application and applicable standards.

Cleanroom HVAC Maintenance

Regular maintenance is essential to maintain HVAC performance.

Typical maintenance activities include:

• AHU inspection
• Pre-filter replacement
• Fine-filter replacement
• HEPA filter inspection
• HEPA integrity testing where required
• Cooling-coil cleaning
• Drain-pan cleaning
• Condensate-drain inspection
• Fan inspection
• Motor inspection
• Belt inspection where applicable
• Sensor calibration
• Differential-pressure monitoring
• Damper inspection
• Duct inspection
• BMS/control-system checks

A preventive-maintenance schedule should be developed according to the equipment and facility requirements.

Applications of Cleanroom AHU Systems

Cleanroom AHU systems can be used in a wide range of industries.

Pharmaceutical Industry

For pharmaceutical manufacturing, formulation, packaging and controlled production areas.

Biotechnology

For laboratories and controlled biological processes.

Electronics & Semiconductor

For manufacturing environments requiring control of airborne particulate contamination.

Medical Device Manufacturing

For controlled manufacturing and assembly areas.

Hospitals

For operating theatres, specialized treatment areas and other controlled environments.

Laboratories

For research and testing facilities requiring controlled environmental conditions.

Food & Beverage

For selected controlled processing and packaging applications.

Cosmetics

For controlled production and packaging environments.

Why Choose Vipul HVAC Solution Pvt Ltd?

Vipul HVAC Solution Pvt Ltd provides HVAC engineering and contracting solutions for cleanrooms, pharmaceutical facilities, hospitals, industrial buildings and other specialized environments.

Our Cleanroom HVAC Services

• Cleanroom AHU
• Cleanroom HVAC design
• Pharmaceutical HVAC
• GMP HVAC systems
• HEPA filtration
• Cleanroom ventilation
• Temperature control
• Humidity control
• Pressure-control systems
• HVAC ducting
• AHU installation
• HVAC controls
• BMS integration
• Air balancing
• Testing and commissioning
• HVAC maintenance and AMC

Integrated HVAC Approach

We consider the complete system rather than the AHU alone:

AHU → Filtration → Ductwork → HEPA → Air Distribution → Pressure Control → Monitoring → Commissioning

This approach helps ensure that individual HVAC components work together according to the project’s cleanroom requirements.

Our Cleanroom HVAC Project Process

1. Requirement Assessment

We review the cleanroom layout, room functions, process requirements and environmental conditions.

2. HVAC Load Calculation

Cooling and ventilation requirements are calculated based on project parameters.

3. Airflow Calculation

Supply, return, fresh-air and exhaust requirements are established.

4. Filtration Selection

Appropriate filtration stages are selected according to the application.

5. AHU Selection

AHU airflow, cooling capacity, fan static pressure and filtration requirements are evaluated.

6. Duct Design

Ductwork is designed for the required airflow and pressure conditions.

7. Installation

AHUs, ducts, piping, controls and filtration systems are installed.

8. Testing & Commissioning

The complete HVAC system is balanced, tested and commissioned according to the project requirements.

Benefits of a Properly Designed Cleanroom AHU

A properly engineered cleanroom AHU system can help provide:

• Controlled air cleanliness
• Stable temperature
• Controlled humidity
• Appropriate airflow
• Controlled pressure relationships
• Effective particulate filtration
• Consistent environmental conditions
• Better process control
• Reliable HVAC operation
• Improved monitoring and maintenance

Actual cleanroom performance depends on proper design, installation, operation, maintenance and testing.