What Makes a Cleanroom a Clean Room?

Cleanroom Vacuum

What is a Cleanroom?

A cleanroom is an area free of impurities, where contamination, air velocity, pressure, temperature, and humidity are controlled under rigid specifications.

Imagine if the medication we ingest and the electronic components we use were produced in rooms populated with chemical vapors, dust, and airborne particulates. These impurities would settle on capsules and circuits and contaminate them. Instead, manufacturers create a controlled environment—a cleanroom—to limit exposure to contaminants.

While not always sterile, a cleanroom follows accepted standards for maximum particulates per cubic meter. Air is filtered in and recirculated through HEPA air filters. Equipment is designed to generate minimal air impurities. Employees wear gloves, face masks, and head covers. Often, donning jumpsuits or smocks is also necessary. The room is cleaned daily, sometimes every few hours, according to rigorous quality procedures.

Things to consider when planning a cleanroom:

  • Rate of personal emission
  • Amount of physical movement
  • Hot and cold environments create different rates of particulate generation
  • Type of undergarments worn
  • Contamination from the tools used
  • FDA regulations

Cleanroom Standards

The most commonly used standard for cleanrooms is the Federal Standard 209E. This standard refers to several classes of cleanrooms and correlates with ISO 14644-1 classes as well. A cleanroom class is determined by the number of particles present per unit volume. A class is met if the measured concentration is within the limits of a specified particle size. For example, typical room air, classified as ISO 9, contains more than 35 million microns of particulates per cubic meter. By contrast, a Federal Standard 209E Class 100 (ISO 5) cleanroom contains a maximum of only 3,520 microns per cubic meter of particulates.

Higher purity cleanrooms raise the standard even further. A Federal Standard 209E Class 1 (ISO 3) cleanroom holds a maximum of only 35 microns per cubic meter of particulates. Consult the Institute of Environmental Sciences and Technology (iest.org) for updates in standards.

Airborne Particulate Cleanliness Classes and ISO Standards

Use this table to convert from English to metric classes and the equivalent ISO standard.

Class name Particle count
ISO standard US SI
ISO 3 Class 1 M 1.5 1
ISO 4 Class 10 M 2.5 10
ISO 5 Class 100 M 3.5 100
ISO 6 Class 1000 M 4.5 1000
ISO 7 Class 10,000 M 5.5 10,000
ISO 8 Class 100,000 M 6.5 100,000
*Particles 0.5 microns or larger in a cubic foot of air.

Keeping a Cleanroom Clean

An extensive list of products and equipment are necessary to set up and maintain a cleanroom. These can be categorized as:

  • Cleaning Equipment: Use vacuums that can be safely operated around electrical equipment and include HEPA and other filters. Some vacuums offer a multi-stage filtration system to capture more than 99% of dust and debris. Adhesive rolls and mops with low contamination characteristics are also suitable for keeping cleanroom walls and floors clean.
  • Consumables: Low particulate wipes and cleanroom swabs help keep small surface areas clean. Multi-layer mats are coated with a particle-grabbing adhesive and an antimicrobial agent to prevent bacterial growth. Adhesive mats can be placed at entrances to extract particulates from shoes and carts. Cleanroom notebooks have polyethylene binding to reduce paper fiber. Cleanroom paper is made without organic fillers to substantially reduce the risk of particle generation. Polypropylene labels are ESD-safe and virtually free of particulates, leechables, and outgases.
  • Testing Equipment: Particle counters test air contamination and are calibrated to meet the Federal Standard 209E. Anemometers and thermoanemometers monitor air flow rates and direction. Ventilation test instruments can measure various parameters including temperature, humidity, carbon dioxide, and more. Air measurement meters test all-around air quality including velocity, volume flow, and temperature. Similarly, air velocity/pressure meters measure pressure drops across filters and test fan and blower discharge and inlet pressures, as well as air velocity in ducts.
  • Apparel: Some wearables are designated specifically for cleanrooms such as cleanroom gloves or antistatic finger cots, which state their ISO compliance level. Boot covers with a microporous film layer reduce particle counts from shoes. Cleanroom garments such as frocks and coveralls offer superior particulate and light barrier protection.
  • Furniture: Chairs, stools, and worktables may be specially designed for use in semiconductor, bioscience, pharmaceutical, and board manufacturing in cleanrooms.


Controlling contamination takes vigilance. That's why cleanrooms are created using strict protocol and methods. From spills and leaks to hair to cleaning chemicals, the potential for impurities to pollute this environment is immense. With specially chosen products and equipment—and the commitment to adhering precisely to protocols—cleanrooms can live up to their standards.

Learn More About Cleanrooms

Cleanroom Weighing: Choosing the Right Scale for the Most Critical Applications
Using Masterflex® L/S® and I/P® Process Pumps in ISO Class 5 (Class 100) Cleanroom Applications