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Cleanroom HVAC Design, Explained: Exploring Key Components

Written by Encompass | May 13, 2025 7:06:39 PM

HVAC systems are arguably the most critical aspect of cleanroom design. These systems influence nearly every factor within a contamination-controlled environment, including temperature, humidity, airflow, and particulate removal for cleanliness. 

Not only is it important, but cleanroom HVAC design and installation is often the most complex aspect of the process. It requires a high degree of customization to suit the unique needs of your cleanroom—from room size and layout to specific process and manufacturing requirements. 

Unlike conventional HVAC systems used in commercial settings, cleanroom HVAC systems must meet stringent cleanliness standards and undergo advanced engineering to achieve precise environmental control and particulate filtration.

What Are HVAC Systems for Cleanrooms?

HVAC stands for Heating, Ventilation, and Air Conditioning. While it’s a broad term, in cleanroom applications, HVAC systems vary greatly depending on the specific environmental controls critical to your operation’s contamination-sensitive needs. 

In general, cleanroom HVAC systems help maintain the required level of airborne particulate cleanliness by constantly filtering and cycling air. The exact design of your cleanroom HVAC varies depending on your facility’s industry, compliance requirements, operational processes, environmental variables, and more.

In some scenarios, an existing HVAC system is sufficient for the level of contamination control needed. A cleanroom can be designed to integrate with this existing system. Similarly, your existing system can be upgraded or enhanced if necessary to meet contamination control standards. In other cases, a purpose-built system must be installed to meet stringent requirements. Regardless, your HVAC must be capable of maintaining tight control over temperature, humidity, airflow, and cleanliness.

How Do Cleanroom HVAC Systems Differ From Conventional?

Cleanroom HVAC systems differ significantly from traditional commercial HVAC units. While standard systems typically operate with 2-4 air changes per hour, cleanroom environments can require up to 250 or more air changes per hour. Additionally, cleanroom HVAC systems continuously circulate filtered air and can remove particles as small as 0.3 microns—something conventional HVAC systems are not designed to do. These cleanroom-specific demands make expert design and engineering essential.

Understanding the Parts of a Cleanroom HVAC System

A cleanroom HVAC system is composed of multiple interdependent components working together to maintain strict environmental control. The three main components include the air filtration system, air flow system, and temperature and humidity controls.

Air Filtration System

Cleanroom HVAC systems are built with advanced filtration capabilities to capture airborne contaminants, including tiny particles and microorganisms. The most common filters used in cleanroom environments include:

  • HEPA (High-Efficiency Particulate Air) Filters: These can trap 99.97% of particles that are 0.3 microns or larger.
  • ULPA (Ultra-Low Penetration Air) Filters: Designed to catch even smaller particles with greater efficiency.

These filters serve as the foundation for particle control, ensuring air entering and recirculating through the cleanroom meets cleanliness standards. The filtration system may also include:

  • Air Locks with HEPA Filters: Prevent cross-contamination by filtering air in transition zones.
  • Pre-Filters: Installed upstream of HEPA filters to capture larger particles and extend filter life.

Air Flow System

The airflow system is responsible for creating a consistent and unidirectional flow of filtered air that keeps harmful particles out of your contamination-free environment. This is achieved through supply and exhaust ducts, air diffusers and grilles, and specific airflow designs.

Cleanrooms can utilize either positive or negative pressure systems:

  • Positive Pressure Systems: Keep contaminants out by maintaining higher pressure inside the cleanroom than in adjacent spaces.
  • Negative Pressure Systems: Prevent contaminants from escaping, typically used in hazardous environments.

To support effective airflow management, cleanroom HVAC systems often incorporate:

  • Constant Air Volume Systems: Maintain steady airflow to minimize particulate accumulation.
  • Pressure Sensors and Control Systems: Adjust pressure automatically to meet cleanroom classifications.
  • Advanced Ductwork: Engineered to direct airflow, control pressure, minimize noise, and improve energy efficiency.
  • Insulated Ducts: Prevent energy loss and maintain stable environmental conditions.

Temperature and Humidity Controls

Temperature and humidity directly affect particle behavior and microbial growth, making their control critical. These elements can work together to provide a stable, contamination-resistant climate tailored to your cleanroom’s operational needs:

  • Heating Components: Boilers or electric heaters warm air through coils in the Air Handling Unit (AHU).
  • Cooling Equipment: Chilled water systems or AC units remove excess heat from the air.
  • Temperature Sensors and Controls: Continuously monitor and adjust the indoor temperature.
  • Humidity Control Systems: Include humidifiers, dehumidifiers, and desiccant systems to maintain optimal humidity levels.
  • Insulation: Reduces temperature fluctuations and conserves energy throughout the duct network.

The Role of Cleanroom HVAC in Compliance

Cleanroom HVAC systems are integral to achieving ISO and regulatory compliance. The cleanroom’s classification determines the required air cleanliness level, typically defined by ISO 14644-1 standards.

Manufacturing cleanrooms are often designed to meet ISO Class 7 or 8 standards, where airflow, temperature, and particulate control are moderate. HVAC systems in these environments don’t require extremely strict temperature or humidity control but must support adequate air filtration and circulation.

Pharmaceutical cleanrooms require tighter control to comply with USP and FDA regulations. ISO Class 7 or cleaner is usually mandated. These environments need precise temperature and humidity control to ensure product stability, especially in regions with wide temperature fluctuations.

Medical device and laboratory cleanroom environments also demand strict particulate control. HVAC systems must be capable of frequent air changes and high-efficiency filtration to meet ISO 14644 classifications, ensuring no contaminants compromise sensitive operations.

In these industries and others, HVAC design plays a pivotal role in maintaining compliance. Whether your space needs 30 air changes per hour or 250, the HVAC system must be built to meet those exacting standards. The Encompass Cleanrooms experts are well-versed across industries and can recommend customizations to suit your regulatory requirements.

How to Properly Maintain Your Cleanroom HVAC System

Maintenance is key to ensuring your HVAC system continues to perform at optimal levels. Regular inspections, cleanings, and component replacements help maintain cleanliness and compliance over time.

Best practices include:

  • Filter Maintenance: Replace HEPA and ULPA filters as needed, and consider using pre-filters to reduce larger particles and extend filter life.
  • Sensor Calibration: Regularly ensure temperature, humidity, and pressure sensors are functioning accurately.
  • System Inspections: Conduct consistent checks on ductwork, fans, and AHUs for any signs of wear, blockage, or inefficiency.
  • Static Pressure and Dampers: Maintain proper static pressure and verify that dampers are functioning to direct airflow correctly.
  • Insulation Checks: Examine insulation for deterioration to prevent heat gain/loss and maintain energy efficiency.

These practices ensure your HVAC system continues to meet the cleanroom's environmental and cleanliness requirements, minimizing operational risks and maximizing system lifespan. The Encompass Cleanrooms team can also assist with maintenance needs.

Trusted Cleanroom HVAC Design, Installation, and Maintenance Experts

Cleanroom HVAC systems require precision design, expert installation, and diligent maintenance to perform at required levels across industries. At Encompass Cleanrooms, our expertise goes beyond cleanroom construction—we are deeply skilled in the engineering and technical implementation of cleanroom HVAC systems.

Our team is equipped to assess and evaluate your existing HVAC infrastructure, recommend system modifications to improve performance and compliance, and design and install fully customized cleanroom HVAC systems tailored to your environment. Whether you’re building a new cleanroom or upgrading an existing one, get in touch with us today for your HVAC needs.