Cleanroom HVAC Design

A cleanroom’s HVAC system is truly the most vital and complex component system of a cleanroom facility.  HVAC…an acronym for Heating, Ventilation, and Air Conditioning…generally describes the idea of providing indoor environmental comfort by creating and controlling indoor air quality (cleanliness, air changes per hour, temperature, humidity and pressure).


Here are some highlights that summarize how cleanroom HVAC systems are unique:

Cleanroom HVAC vs. Conventional HVAC

In addition to creating a comfortable environment…Cleanroom HVACs specifically focus on:

  1. Increased Air Supply
  2. Airflow Patterns
  3. High Efficiency Filters
  4. Room Pressurization
  5. Regulations & Cleanliness level guidelines
  6. Temperature & Humidity Control
  7. Accounting of processes taking place inside the cleanroom
  8.  Specialized Ventilation Duct Expertise

HVAC System vs. HVAC Unit

HVAC systems and their component HVAC air handling units (AHU) are sometimes confused. The air handler is simply the enclosure in which the air is heated, filtered, and cooled. It includes DX cooling coils, chilled water coils, electric heat or hot water heat coils and humidifiers. The HVAC system is, as its name spells out, the whole system, which includes the air handling unit, but also the duct work, the diffuser, the HEPA filters, the air return, and the control and monitoring system.

Choose/Design the appropriate system

The required cleanliness level of the cleanroom (ISO class) is the key driver of the HVAC design process…in addition to the required temperature, humidity, and pressure differential. These conditions are dictated by the processes taking place in the cleanroom and the required comfort of the personnel working inside the room.

Air Flow (CFM)

The most important bit of information needed to begin the Cleanroom HVAC design process  (by your cleanroom supplier/manufacturer) is:

How many air changes per hour is needed in your cleanroom in order to calculate the required air flow? (CFM: cubic feet per minute).

Though difficult to determine, the answer must take into account the following elements:

  • Cleanliness level (number of particles per cubic foot of air) the cleanroom must be kept within: often determined by the cleanroom class (ISO 5-6-7-8, GMP A-B-C, etc.)
  • Number of people working in the cleanroom
  • Size of the cleanroom and the number of rooms inside
  • Equipment, furniture, and supplies inside the cleanroom since they generate air particulates and contamination
  • Heat gain
  • Movement of people and material in and out of the cleanroom

Temperature and Humidity

The heat produced by both the users and the equipment must be compensated by the air conditioning. Therefore, it is important to know how many people will be working in the cleanroom, the equipment in place and the heat it generates (watt).

Pressure Differential

The HVAC system is responsible for creating pressure differentials to keep pressure cascades in between the divisions of the cleanroom and the outside of the cleanroom.  Most cleanrooms are held in positive pressure. This means that the air will flow out of the room instead of in, thus preventing unfiltered air or air particulates from entering the cleanroom.  When dealing with hazardous products however, the cleanroom must be held in negative pressure.


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