What is Cleanroom

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A clean room is a room where the concentration of particles is minimized. Temperature, humidity and pressure parameters are also controlled.

Operators use particular clothes (foot booties, coat, hairnet and gloves) to avoid dirtying the room.

Clean rooms are used for the industry or research fields, which are sensible domains to environmental contamination (biology, construction of spacecraft, optical manufacturing or semiconductors…).

To cope with rising demands of optics and space applications, an ISO 7 (class 10 000) clean room has been installed to minimize the presence of particles such as dust to enable the integration of “clean” and vacuum compatible hexapods.

In the space sector, we regularly deliver ISO 5 compatible systems, for which we follow the design and assembly rules related to the cleanliness of the ISO 5 environment.

A cleanroom or clean room is an engineered space, which maintains a very low concentration of airborne particulates. It is well isolated, well-controlled from contamination, and actively cleansed. Such rooms are commonly needed for scientific research, and in industrial production for all nanoscale processes, such as semiconductors & medicine manufacturing. A cleanroom is designed to keep everything from dust to airborne or vaporized particles, away from it, and so from whatever material is being handled inside it.

Cleanrooms typically come with a cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger, equivalent to an ISO 9 certified cleanroom. By comparison an ISO 14644-1 level 1 certified cleanroom permits no particles in that size range, and just 12 particles for each cubic meter of 0.3 μm and smaller. Semiconductor facilities often get by with level 7, while level 1 facilities are exceedingly rare.

Some cleanrooms are kept at a positive pressure so if any leaks occur, air leaks out of the chamber instead of unfiltered air coming in. This is most typically the case in semiconductor manufacturing, where even minute amounts of particulates leaking in could contaminate the whole process, while anything leaking out would not be harmful to the surrounding community. The opposite is done e.g. in the case of high level bio-laboratories, handling contaminous viruses; those are always held at negative pressure, with the exhaust being passed through high efficiency filters, and further sterilizing procedures. Both are still cleanrooms, because the particulate level inside is maintained within very low limits.

Some cleanroom HVAC systems control the humidity to such low levels that extra equipment like air ionizers are required to prevent electrostatic discharge problems. This is a particular concern within the semiconductor business, because static discharge can easily damage modern circuit designs. On the other hand, active ions in the air can harm exposed components as well. Because of this most workers in high electronics and semiconductor facilities have to wear conductive boots while working. Low-level cleanrooms may only require special shoes, with completely smooth soles that do not track in dust or dirt. However, for safety reasons, shoe soles must not create slipping hazards. Access to a cleanroom is usually restricted to those wearing a cleanroom suit, including the necessary machinery.

In cleanrooms in which the standards of air contamination are less rigorous, the entrance to the cleanroom may not have an air shower. An anteroom (known as a “gray room”) is used to put on clean-room clothing. This practice is common e.g. in many nuclear power plants, which operate as low-grade inverse pressure cleanrooms, as a whole.

Recirculating vs. One pass cleanrooms

Recirculating cleanrooms return air to the negative pressure plenum via low wall air returns. The air then is pulled by HEPA fan filter units back into the cleanroom. The air is constantly recirculating and byu continuously passing thru HEPA filtration removing particles from the air each time. Another advantage of this design is air conditioning can be incorporated.

One pass cleanrooms draw air from outside the cleanroom, pass it thru HEPA fan filter units into the cleanroom. The air then leaves thru exhaust grills to outside the cleanroom. The advantage of this approach is the lower cost. The disadvantages are short HEPA fan filter live, worse particle counts than similar recirculating cleanroom, and cannot accommodate air conditioning.

Clean room Classification

ClassMaximum particles/m3FED STD 209E equivalent
≥0.1 µm≥0.2 µm≥0.3 µm≥0.5 µm≥1 µm≥5 µmCleanroom
ISO 110
ISO 21002410
ISO 31 00024710235Class 1
ISO 410 0002 470102035283Class 10
ISO 5100 00024 70010 2003 520832Class 100A
ISO 61 000 000247 000102 00035 2008 320293Class 1 000B
ISO 7352 00083 2002 930Class 10 000C
ISO 83 520 000832 00029 300Class 100 000D
ISO 935 200 0008 320 000293 000Room air
GradeMaximum limits for total particle ≥0.5µm/m³Maximum limits for total particle ≥0.5µm/m³Maximum limits for total particle ≥5.0µm/m³

Maximum limits for total particle ≥5.0µm/m³

At restIn operationAt restIn operation
A3,5203,520Not specifiedaNot specifieda
B3,520352,000Not specifieda2,930
D3,520,000Not predeterminedb29,300Not predeterminedb

Classification including 5µm particles may be considered where indicated by the CCS or historical trends.

b For grade D, in operation limits are not predetermined. The manufacturer should establish in operation limits based on a risk assessment and routine data where applicable.


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