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Cleanliness Classification Guide: Core Standards and Industry Applications Explained
2026/9/16
I. Core Classification Standard System Analysis
Currently, the division of clean areas is mainly based on the concentration of suspended particles in the air, combined with microbial control requirements. There are three main mainstream standard systems in the international and domestic fields:
1. International General Standard (ISO 14644-1 / GB/T 25915.1)
This is the most authoritative cleanliness classification standard globally. The Chinese national standard GB/T 25915.1-2021 and others have equivalent adopted this system. This standard uses the number of suspended particles ≥ 0.1 μm and ≥ 0.5 μm per cubic meter of air as the sole determination indicator, dividing cleanliness into ISO 1 level to ISO 9 levels. The smaller the number, the higher the cleanliness. For example, ISO 5 level requires that the concentration of ≥ 0.5 μm particles does not exceed 3,520 per m³, while ISO 8 level relaxes this to 3,520,000 per m³.
2. Pharmaceutical Industry Exclusive Standard (GMP A/B/C/D Classification)
The pharmaceutical and biopharmaceutical industries not only focus on suspended particles but also emphasize the dynamic control of microorganisms (floating bacteria, settling bacteria). The Chinese GMP (2010 edition) divides clean areas into four grades: A, B, C, and D. Among them, grade A is the high-risk operation area (such as aseptic filling), with dynamic standards corresponding to ISO 5 level; B is the background environment of grade A; C and D levels are used for secondary areas of aseptic production and non-aseptic operation areas, corresponding to ISO 7 to ISO 8 levels.
3. Traditional Industry Customized Classification (US FS 209E System)
Although the US Federal Standard FS 209E has been abolished, terms like "hundred-level," "thousand-level," "ten thousand-level," and "hundred thousand-level" are still widely used in the industrial sector. These nicknames have a clear correspondence with the ISO standards: hundred-level corresponds to ISO 5 level, thousand-level corresponds to ISO 6 level, ten thousand-level corresponds to ISO 7 level, and hundred thousand-level corresponds to ISO 8 level. Understanding this correspondence can help avoid misunderstandings in cross-industry communication.
II. Differentiated Applications in Key Industries
Different industries have significant differences in their core demands for clean areas due to the characteristics of their products:
1. Semiconductor and Microelectronics Industry: Control of Micro Particles and Anti-static
This industry has the "ceiling" of cleanliness requirements. Core processes such as lithography and etching in high-end chips usually require extremely high cleanliness environments of ISO 3 to ISO 5 (tens of levels to hundreds of levels) to prevent micro particles from causing short circuits or performance degradation. In addition, electronic clean rooms need to strictly control temperature and humidity accuracy, micro-vibration, and gas molecule pollution (AMC), and be equipped with complete anti-static (ESD) systems.
2. Pharmaceutical and Biopharmaceutical Industry: Sterility and Microbial Dual Control
The core of the pharmaceutical industry is to prevent microbial contamination and cross-contamination. Sterile injectables and vaccines must be produced in GMP A/B level environments, using single-stream ( laminar flow) design and equipped with VHP ( vaporized hydrogen peroxide ) and other sterilization equipment. For low-risk products such as oral solid preparations and capsules, they are usually produced in D level (hundred thousand-level) environments.
3. Medical Devices and Food Industry: Risk Grading Control
Medical devices are classified based on risk levels: implantable high-risk devices (such as heart stents, artificial joints) require ISO 5-6 level environments; For disposable consumables, masks and other types of equipment, ISO 7-8 grades are sufficient to meet the requirements. In the food industry, emphasis is placed on pathogenic bacteria and dust control. High-risk foods such as infant milk powder and sterile beverages need to reach standards of hundreds to thousands of levels, while ordinary baking and grain processing are carried out in environments ranging from 100,000 to 300,000 levels.
III. Key points of operation and maintenance of clean areas
Regardless of the level, the stable operation of a clean room cannot be achieved without strict control of the following three environmental parameters:
Pressure difference control: To prevent external contaminated air from infiltrating, a static pressure difference of ≥ 5 Pa must be maintained between different clean-level areas, and the pressure difference between the clean area and the non-clean area should be ≥ 10 Pa. Air flow organization and air change rate: High-level clean areas (such as ISO 5 level) usually adopt unidirectional flow ( laminar flow) design, with air change rates as high as over 240 times per hour; while low-level areas (such as ISO 8 level) mostly adopt non-unidirectional flow, with air change rates ranging from 10 to 25 times per hour. Temperature, humidity and illumination: The temperature in a regular clean area is controlled at 22℃ ± 2℃, the relative humidity at 50% ± 5% RH, and the main working area illumination should be no less than 150 lux. Special industries (such as lithium batteries, semiconductors) have additional requirements for extremely low humidity (dew point ≤ -40℃).
Conclusion
The classification of cleanliness is not about "the higher the better", but rather it needs to be matched with the production process, product risks, and construction costs. When designing and inspecting clean workshops, enterprises should first clearly define the industry norms they belong to (such as GMP or ISO), accurately define the dynamic and static testing conditions, and establish a complete daily particle and microorganism monitoring system, so as to ensure the continuous compliance of the production environment and the stability and reliability of product quality.
