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The clean room can also be called dust free room. It is the special designed room, in which the pollutants in the air such as micro particle, harmful gas and bacterium are removed away and the room characteristics must be controlled in a certain level, such as temperature, cleanliness, the pressure in the chamber, airflow velocity and distribution, noise, vibration, illumination and static electricity.

No matter how the external air conditions change, the interior of the clean room can still keep the original set level of properties including cleanliness, temperature, humidity, pressure and others. The main function of the clean room is to control the cleanliness, temperature and humidity of the air of the environment that the product such as silicon chip stays in. Then, the product can be produced in a good environment.

FS 209E ISO 14644-1
Maximum Allowable Limit Value of Particle Concentration (≥D)Pc/m3 Allowable Limit Value of Particle Concentration(≥D)Pc/m3
Particle Diameter (um) Level 0.1 0.2 0.3 0.5 5.0 Particle Diameter (um) Level 0.1 0.2 0.3 0.5 1.0 5.0
ISO1 10 2
ISO2 100 24 10 4
M1 350 (9.91) 75.7(2.14) 30.9(0.875) 10(0.283)
M1.5 1240(35) 265(7.5) 106(3) 35.3(1.0) ISO3 1000 237 102 35 8
M2 3500(99.1) 757(21.4) 309(8.75) 100(2.83)
M2.5 12400(350) 2650(75) 1060(30) 353(10) ISO4 10,000 2370 1020 352 83
M3 35,000(991) 7570(214) 3090(87.5) 1000(28.3)
M3.5(100) 26,500(750) 10600(300) 3530(100) ISO5 100,000 23700 10,200 3520 832 29
M4 75,700(2140) 30900(875) 10,000(283)
M4.5(1000) 35300(1000) 247(7) ISO6 1,000,000 23,7000 102,000 35,200 8320 293
M5 100,000(2830) 618(17.5)
M5.5(10000) 353,000(10,000) 2470(70) ISO7 352,000 83,200 2930
M6 1,000,000(28,300) 6180(175)
M6.5(100000) 3,530,000(100,000) 24,700(700) ISO8 3,520,000 832,000 29,300
M7 10,000,000(283,000) 61,800(1750)
ISO9 35,200,000 8,320,000 293,000

Note
1. The number in the brackets is the British imperial particle concentration with the unit of Pc/ft3.
2. The name for the table with ISO 14644-1 should be The Selected Clean Room Suspended Particle Cleanliness Level according to the standard.

Every country has its own specification for the cleanliness class, but the most frequently used standard is the American federal standard of 209. Then, we just introduce the standards of 209D, 209E and of the other country.

The largest difference between the standard of 209E and the other standards such as 209 is that the representation unit of 209E has the metric unit included. The clean room level is expressed with the first letter of M, such as M1, M1.5, M2, M2.5, M3 and so on. It is stipulated to match with the standardization of international metric unit. The Arab number after the M is calculated in this way. First, we measure the concentration of dust particle for per cubic meter. The diameter of the particle is not less than 0.5μm. The number of the dust particle is showed with the bottom number of 10. Then the power exponent is the number after the M. If the dust particle number is a middle value between two numbers with power, then the number after M is expressed with 1.5, 2.5, 3.5 and so on.

The American federal standard of 209D adopts the Pc/ft3 as the unit. But the Japanese standard uses the metric unit and the counting standard is the particles with the diameter of 0.1μm. Then the cleanliness level is expressed with Class 1, Class 2 to Class 8. The highest level is Class 1 and the least level is Class 8. The dust particle number is counted with the unit of Pc/m3 and is expressed in the way of 10 to the power of n. Then the n is the number in the level.

The management and control for clean room of our company often involves in the following aspects
1. It can remove the dust particles drifting in the air and the harmful gas and avoid the generation of the dust particles.
2. It can not only control the temperature and humidity but also adjust the pressure in the room.
3. The air tightness between the structure and compartment can be assured.
4. The static electricity should be prevented. Meanwhile, the clean room can also prevent electromagnetic interference.
5. The security and energy saving are also considered to construct the clean room.

The main projects that we can conduct are listed as follows
1. The clean engineering for the plants of industry, electron, cosmetic, fiber optic communication, silk-screen printing.
2. The purification engineering for GMP factory, pharmaceutical factory, food products plant and canning workshop of drink water plant.
3. The overall planning, design and construction for laboratory project, sterile laboratory and biological laboratory.
4. The installation, debugging, repair and maintenance for central air conditioning and purification engineering equipment.
5. The air conditioning cleaning project, clean room construction and renovation project for plant, workshop and laboratory.
6. The wall project, ceiling work, ground engineering and other small engineering in the interior of industrial plant.

The clean room mainly has the turbulent flow type and laminar flow type.

1. Turbulent flow clean room
The air enters into the clean room through the air duct of air conditioning box and the high efficiency particulate air filter in the clean room. Then, the air is returned by the wall panels of the compartments at the two sides of clean room or the elevated floor. For the non-linear movement, the air flow appears to be irregular turbulent flow or eddy flow. This structure is fit for the clean room with the cleanliness level of 1000 to 100000.

The turbulent flow clean room has simple structure and low system construction cost. Meanwhile, the expansion for the clean room is easy. In some special occasions, it can also be used in conjunction with clean bench to enhance the cleanliness level. But there are also some shortages of the clean room. The dust particles caused by the turbulent flow drift in the room and cannot be removed away easily, which is easy to pollute the products. Meanwhile, if the user needs to activate the system again after it has already stopped operation, it often costs quite a long period of time to reach the needed cleanliness level.

2. Laminar flow clean room
The air flow movement forms a uniform plane and the air enters into the room through the air filter with the coverage rate of 100%. Then it is returned via the elevated floor or the wall panels at two sides. This structure is suitable for the clean room with high requirement for cleanliness level which is generally from Class 1 to Class 100. This type of structure can also be divided into two kinds.

A. Horizontal laminar flow type
The horizontal air is discharged from air filter with single direction and is returned through the air return system at the wall of the other side. Then the dust is removed out of the room with the air flow. The pollution is often serious at the down stream. The advantages of this type of clean room are that its structure is simple and it can be in a stable state after running in a short period of time. But the construction cost is high than that of turbulent flow type and it is not easy to expand the interior space.

B. Vertical laminar flow type
The ceiling of the room is covered with the ultra low penetration air filter completely. The air blows from top to bottom. The dust particles generated during the production process or by the working staff can be quickly exhausted to the outside and won't affect the other working areas. The cleanliness in the room is comparatively high.

This type of clean room can be managed easily. It can stay in a steady state only after running a short period of time. Meanwhile, it won't be affected easily by the working status or the working staff. But the construction cost is high. In addition, the suspension bracket of the ceiling needs to occupy large space. It is difficult to use the space flexibly. What's more, it is particularly inconvenient to repair and replace the air filter.

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