Cleanroom
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Overview
Cleanrooms can be very large. Entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. They are used extensively in semiconductor manufacturing, biotechnology, the life sciences and other fields that are very sensitive to environmental contamination.
The air entering a cleanroom from outside is filtered to exclude dust, and the air inside is constantly recirculated through high efficiency particulate air (HEPA) and ultra low penetration air (ULPA) filters to remove internally generated contaminants. Staff enter and leave through air locks (sometimes including an air shower stage), and wear protective clothing such as hats, face masks, boots and cover-alls. Equipment inside the cleanroom is designed to generate minimal air contamination. Common materials such as paper, pencils, and fabrics made from natural fibers are often excluded. Low-level cleanrooms are often not sterile (i.e., free of uncontrolled microbes) and more attention is given to airborne dust.
Cleanroom HVAC systems often control the humidity to low levels, such that extra precautions are necessary to prevent electrostatic discharges.
Cleanroom classifications
The following is adapted from Rockwell Automation (http://www.rockwellautomation.com/anorad/guide/cleanroom_criteria.html):
US FED STD 209E cleanroom standards
| particle/ft³ | ||||||
| Class | 0.1 µm | 0.2 µm | 0.3 µm | 0.5 µm | 1 µm | 5 µm |
| 1 | 35 | 7 | 3 | 1 | ||
| 10 | 350 | 75 | 30 | 10 | 1 | |
| 100 | 750 | 300 | 100 | 10 | 1 | |
| 1,000 | 1,000 | 100 | 10 | |||
| 10,000 | 10,000 | 1,000 | 100 | |||
| 100,000 | 100,000 | 10,000 | 1,000 | |||
ISO 14644-1 cleanroom standards
| particle/m³ | ||||||
| Class | 0.1 µm | 0.2 µm | 0.3 µm | 0.5 µm | 1 µm | 5 µm |
| ISO 1 | 10 | 2 | ||||
| ISO 2 | 100 | 24 | 10 | 4 | ||
| ISO 3 | 1,000 | 237 | 102 | 35 | 8 | |
| ISO 4 | 10,000 | 2,370 | 1,020 | 352 | 83 | |
| ISO 5 | 100,000 | 23,700 | 10,200 | 3,520 | 832 | 29 |
| ISO 6 | 1,000,000 | 237,000 | 102,000 | 35,200 | 8,320 | 293 |
| ISO 7 | 352,000 | 83,200 | 2,930 | |||
| ISO 8 | 3,520,000 | 832,000 | 29,300 | |||
| ISO 9 | 35,200,000 | 8,320,000 | 293,000 | |||
Cleanroom class comparison
| ISO 14644-1 | FED STD 209E |
| ISO 3 | 1 |
| ISO 4 | 10 |
| ISO 5 | 100 |
| ISO 6 | 1,000 |
| ISO 7 | 10,000 |
| ISO 8 | 100,000 |
See also
Cleanroom (Software Engineering)
Cleanroom is also a term used in software engineering.
Meaning 1: The process is based on very careful design of functions. The implementation of these are then peer-reviewed to verify that they do what they are specified to. By analogy with cleanrooms in semiconductor fabrication which prevent the need for cleaning silicon wafers by making sure that they never get dirty, Cleanroom development removes the need for debugging by ensuring that bugs never get introduced. (see also Rational Unified Process).
Meaning 2: Another different use of the term "cleanroom" in software engineering is the use of separate teams to specify requirements, implement functionality, and to compare the two. Communication between the groups is usually carried out only in writing, with all communication being reviewed by lawyers.
This method can be used to develop software in a way that can be demonstrated not to have infringed legal restrictions by a third party. This form of clean-room development was used to develop the first non-infringing third-party PC BIOS implementations.