Clean room 101

Common Clean room Applications:

  • Injection Molding
  • Aseptic Filling and Packaging
  • Electronics Manufacturing
  • Research and Development
  • Medical Device Manufacturing
  • Food and Beverage Production and Packaging
  • Aerospace and Defense
  • Optics and Lasers
  • Packaging and Container Manufacturing
  • Pharmaceutical Manufacturing and Packaging

Cleanroom Classifications and Standards

A cleanroom is classified by the amount of airborne particles within the room. The International Organization for Standardization (ISO) is used to classify a cleanroom based on the size and number of airborne particles per cubic meter of air space.

The US FED STD 209E was previously used to classify cleanroom. In 2001 the General Service Administration canceled this classification, although it is still commonly used today. The FED STD 209E was replaced by the ISO 14644-1. The ISO standards have 9 different classifications of cleanliness as opposed to the 6 classifications in the FED STD 209E, as seen in the chart below.

Cleanrooms Classification

Cleanroom Classification

A US FED STD 209E class 100,000 cleanroom is the dirtiest clean room and is equivalent to an ISO 8 cleanroom. A US FED STD 209E class 1 cleanroom is the cleanest space and is equivalent to an ISO 3 clean room.

The ISO standards added 1 dirtier classification and 2 cleaner classifications. ISO class 9 is the dirtiest space and ISO class 1 is the cleanest space. There are no US FED STD 209E equivalents for ISO 1, ISO 2, or ISO 9 cleanroom.

Clean Room Function & Operation

Positive pressure clean room are designed to keep contaminants from entering the room. Air is introduced into the cleanroom after passing through a fan-powered High-Efficiency Particulate Air (HEPA) filter that will remove the particles in the air. The HEPA fans create air pressure inside of the cleanroom that is greater than the surrounding area preventing contaminants from entering the clean environment. Any contaminants that may be in the air are forced down and directed to filtered return grills located near the floor.

A standard HEPA filter is 99.97% to 99.995% efficient. A ULPA filter, (Ultra-Low Particulate Air) is 99.9995% efficient. Additional filter units may be installed in order to maintain the specified airborne particulate levels by increasing the air change rate inside of the cleanroom.

Negative pressure cleanroom are designed to keep pollutants and contaminants from leaving the room.

Sources of Cleanroom Contamination

Cleanroom contaminants are produced from equipment, processes, building materials, and people inside of the cleanroom. The largest source of contamination is from the employees working in the cleanroom.

Cleanroom Contamination from Employee

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A particle can be defined as a very small mass of solid or liquid matter, typically measured in microns. The largest particle size measured within a cleanroom is 5 microns, for comparison, a human hair is 60 to 90 microns!

Controlling Cleanroom Contamination

There are many factors that contribute to contamination control. The key is to create processes and controls not only within the cleanroom but throughout the entire building or facility. Some of the important factors are:

  • Cleanroom building materials
  • Quality and quantity of HEPA filters
  • Proper clean room design and workflow
  • Cleanroom maintenance and cleaning procedures
  • Properly sized gowning rooms, ante rooms, and airlocks
  • A thorough understanding of your equipment and production or manufacturing process
  • The measurement and instrumentation used in the cleanroom


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