Cleanroom Classification Requirements

A cleanroom is an environment typically used in different laboratories, where low level of environmental pollutants and a high level of sterility is required. It is a ‘contained space’ where arrangements are made to reduce the introduction, production, and storage of particles inside the room and to control other environmental factors such as temperature, humidity, and pressure.

Depending on specific needs, cleanrooms have various levels of contaminants, such as airborne particles, dust particles, and chemical vapors, to be measured in the number of particles per meter. Cleanrooms are widely utilized in the following areas because they are sensitive to environmental contamination:

  • Biotechnology labs
  • Electronic assembly
  • Semiconductor manufacturing
  • Pharmaceutical labs
  • Medical labs


The main objective of a cleanroom is “to maintain a constant environment with controlled levels of airborne particles.”

This can be achieved by taking preventive measures so that contaminated particles and pollutants will not enter the contained spaces. External air entering the environment should be filtered and often kept at a positive pressure so that the unfiltered air will not be entered into the filtered environment.


Cleaning chambers are classified according to the air quality based on the value of 0.5 mm or larger particles per cubic feet or meters consistent with US Federal Standard 209 (A through D). They are classified consistent with the amount and size of particles that are permitted per volume of air. The following is a table shows the various cleanroom classifications based on US Federal Standards:

Class Maximum particles/ft3 ISO equivalent
≥0.1 µm ≥0.2 µm ≥0.3 µm ≥0.5 µm ≥5 µm
1 35 7.5 3 1 0.007 ISO 3
10 350 75 30 10 0.07 ISO 4
100 3,500 750 300 100 0.7 ISO 5
1,000 35,000 7,500 3,000 1,000 7 ISO 6
10,000 350,000 75,000 30,000 10,000 70 ISO 7
100,000 3.5×106 750,000 300,000 100,000 830 ISO 8

The US federal standards were officially canceled in November 2001, with most switching to ISO-14644-1 and ISO 14698 standards that measure the number and size of particles that are permitted per cubic meter of air. The following is the table:

Class Maximum particles/m3 a FED STD 209E equivalent
≥0.1 µm ≥0.2 µm ≥0.3 µm ≥0.5 µm ≥1 µm ≥5 µm
ISO 1 10b d d d d d
ISO 2 100 24b 10b d d e
ISO 3 1,000 237 102 35b d e Class 1
ISO 4 10,000 2,370 1,020 352 83b e Class 10
ISO 5 100,000 23,700 10,200 3,520 832 d,e,f Class 100
ISO 6 1,000,000 2,3700 1,02000 35200 8320 293 Class 1000
ISO 7 3,52000 83200 2930 Class 10000
ISO 8 3520000 832000 29300 Class 100000
ISO 9 35200000 8320000 293000 Class 1000000


For contamination control, both Air Handling and Ventilation are important.

  • The size of the particle-like 0.3 microns and larger (ISO Class 2-9) are controlled by High Efficiency Particulate Air (HEPA) filter.
  • For smaller particles (ISO Class 1) Ultra Low Particulate Air (ULPA) filters are used.

Depending upon the ISO class desired, airflow type, airflow velocity, and air changes are determined by always keeping positive pressure in the cleanroom.


Following is some of the Cleanroom requirements related to ISO Standards.

  • ISO 5- A Cleanroom must have less than 3520 particles>0.5 micron per cubic meter and 250-300 HEPA filtered air changes per hour.
  • ISO 6- A Cleanroom must have less than 35200 particles>0.5 micron per cubic meter and 180 HEPA filtered air changes per hour.
  • ISO 7- A Cleanroom must have less than 352000 particles>0.5 micron per cubic meter and 60 HEPA filtered air changes per hour.
  • ISO 8- A Cleanroom must have less than 35200000 particles>0.5 micron per cubic meter and 20 HEPA filtered air changes per hour.

Various laboratories require cleanrooms and sterile environments to perform their experiments and to produce their products. Following are the three important requirements defined in the Good Manufacturing Practices (GMP) of a cleanroom:

  1. The internal surfaces of the cleanroom and the equipment should be smooth and impervious.
  2. The control and quality of air through the cleanroom; controlled temperature and humidity.
  3. The way the cleanroom is operated and maintained.

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