What is the Difference between Sterile and Clean in a Cleanroom?

In cleanrooms, “sterile” and “clean” are two different concepts, each representing different environmental control requirements and standards. This article can help us better understand the differences between these two concepts.

In cleanrooms


Differences in Definition



Sterile means there are absolutely no living microorganisms in the environment, including bacteria, viruses, fungi, and spores.


Clean refers to strictly controlling the levels of particles and contaminants in the environment within certain limits, but does not guarantee complete sterility.


Differences in Purpose


To completely eliminate all microorganisms, achieving a sterile state.


To reduce contaminants and particles to levels that meet the cleanliness standards for that environment.


Differences in Environmental Requirements


Differences in Environmental Requirements

The environmental requirements are very strict, often requiring a biological safety cabinet, sterile operating rooms, or specialized sterile environments.


Compared to sterile environments, the requirements are not as strict, but precise control of temperature, humidity, pressure, and maintaining the required cleanliness is necessary.


Differences in Implementation


  1. High-temperature, high-pressure sterilization: Using steam at temperatures of 121°C or higher and pressures typically above 15 psi.
  2. Chemical sterilization: Using sterilizing agents such as ethylene oxide, hydrogen peroxide, or chlorine compounds.
  3. Radiation sterilization: Using gamma rays or electron beams.
  4. Filtration sterilization: Filtering liquids or gases through a membrane with micropores to remove microorganisms.




  1. Air filtration: Using HEPA (High-Efficiency Particulate Air) filters or ULPA (Ultra-Low Penetration Air) filters.
  2. Strict cleaning procedures: Regularly cleaning and disinfecting surfaces and equipment.
  3. Airflow design: Using laminar flow or turbulent flow designs to reduce particle accumulation.
  4. Protective equipment: Wearing clean suits, gloves, and masks to reduce contamination from personnel.


Differences in Equipment


Requires sterilization equipment such as autoclaves for high-pressure sterilization, chemical sterilization equipment, and radiation sterilization equipment.


Requires air filtration equipment, cleanroom garments, cleaning supplies, and air circulation control equipment.

Cleanroom Garments

Differences in Verification and Control


  1. Biological load testing: Testing for residual microorganisms in sterile products.
  2. Sterility testing: Culture-based testing to ensure sterile products are free from any microorganisms.
  3. Environmental monitoring: Regularly testing air and surfaces to ensure the ongoing sterility of the environment.


Clean :

  1. ISO 14644 Standard: Divides cleanrooms into ISO classes 1 through 9 based on the concentration of particles in the air.
  2. Federal Standard 209E: Divides cleanrooms into Class 1 to Class 100,000.
  3. Environmental monitoring: Monitoring air quality using particle counters and sampling devices.


Differences in Application Scenarios


Medical and pharmaceutical industries:

Medical and pharmaceutical industries

Sterile injections, operating rooms, sterile medical equipment.


Cell culture, sterile laboratory operations.

Food industry:

Aseptic packaging and preservation.



Electronics and semiconductor industries:

Chip manufacturing, hard drive assembly.


Assembly of precision instruments.

Food processing:

Clean control during packaging and processing.


Case Study

A food processing plant produces high-end infant formula with extremely high requirements for environmental cleanliness and sterility.

Measures Taken:

Clean and Sterile Area Division:

Clean and Sterile Area Division

The production area is divided into clean and sterile areas. Raw material handling and initial processing occur in the clean area, while final packaging occurs in the sterile area.


Environmental Control:

The clean area meets ISO 7 standards (Class 10,000), and the sterile area meets ISO 5 standards (Class 100).

HEPA filters and ULPA filters are used to control air quality in the clean and sterile areas, respectively.


Sterilization and Disinfection:

Production equipment and packaging materials undergo high-temperature, high-pressure sterilization before entering the sterile area.


Personnel Wear Sterile Clothing:

Operators wear sterile clothing and must pass through an airlock chamber for personal cleaning and disinfection before entering the sterile area.


Monitoring and Validation:

Monitoring and Validation

Regular microbiological testing and environmental monitoring are conducted to ensure that the sterile and clean areas meet standards.

Each batch of formula is tested for microbiological contamination to ensure sterility requirements are met.



Through effective clean and sterile management, the plant produces infant formula of stable quality that meets food safety standards, earning consumer trust.



Both sterile and clean environments face risks and challenges in controlling contamination sources, ensuring equipment and processes are reliable, and maintaining continuous monitoring and validation. Although they differ in many aspects, both require a high level of expertise and management measures to maintain and improve environmental cleanliness and sterility. Understanding these differences helps us choose more appropriate environmental control measures to meet specific needs and standards.

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