Dynamic and static testing standards for clean rooms

The following tests should be conducted for the cleanliness of the air in the clean room

(Figure 1: Clean room air cleanliness)

1. Dynamic and static tests

Dynamic test: The clean room has been completed, the Clean air conditioning system is in normal operation, and the test is conducted when there are no process equipment and production personnel in the room.

Static test: The clean air conditioning system in the clean room is in normal operation, the process equipment has been installed, and the test is conducted when there are no production personnel in the room.

2. Dynamic test: The clean room is tested under normal production conditions.

Clean room related parameter detection

1. Preparation before the test

a. The clean room and its clean air conditioning system should be thoroughly cleaned.

b. Use a light scattering particle counter to perform a leak test on the high-efficiency Air Filter. 

First, determine that the number of dust particles with a particle size greater than or equal to 0.5 microns in the static pressure box (or in the air duct) on the upwind side of the high-efficiency air filter should be greater than or equal to 30,000 particles/liter. If it is not enough, smoke can be introduced and then leak detection can be started. The sampling port of the particle counter (or leak detection device) is 2-3 cm away from the high-efficiency air filter, and can be moved at a speed of 2-4 cm/s to scan the entire cross-section of the high-efficiency air filter. The head seal and the installation frame.

When the particle counter reading is that the dust particles greater than or equal to 0.5 microns at the air outlet exceed 3 particles/min·L (or its penetration rate is greater than 0.01‰), it is considered that there is an obvious leakage at this place and it must be plugged.

(Figure 2: Clean room Testing)

2. Test content

• Total air supply volume, total return Air volume, fresh air volume, exhaust volume, etc.;

• Dust-free room pressure value;

• Laminar clean room cross-section Wind speed and airflow direction;

• Cleanliness of clean working area;

• Adjustment test of indoor temperature, humidity and its control ability;

• Clean room noise.

3. Test method for clean working area air cleanliness

For counting dust particles with a particle size greater than or equal to 0.5 microns, the light scattering particle counting method should be used. For counting dust particles with a particle size greater than or equal to 5 microns, the filter microscope counting method can also be used.

Light scattering particle counting method:

a. Sampling volume of light scattering particle counter 

Class 100: Each sampling volume is greater than or equal to 1 liter. 

Class 1,000-10,000: Each sampling volume is greater than or equal to 0.3 liters. 

Class 100,000: Each sampling volume is greater than or equal to 0.1 liter.

For Class 100 Clean rooms, a large flow particle counter should be used for testing; if conditions are not met, a particle counter with a sampling volume of not less than 1 liter per time can be used.

b. Sampling precautions:

• The sampling tube must be clean and leakage is strictly prohibited at the connection.

• The length of the sampling tube should be based on the allowable length of the instrument. When there is no regulation, it should not be greater than 1.5 meters.

• The flow rate at the sampling tube mouth should be close to the average wind speed of the clean room section. The tester should be on the downwind side of the sampling port.

• The sampling sequence should be from low to high dust concentration.

(Figure 3: Air cleanliness detection in clean working area)

c. Measurement point arrangement

• The test is carried out in the clean working area. When there is no special requirement for the production process, the sampling height should be 1 meter from the ground.

• The total number of measurement points in the laminar clean room shall not be less than 20 points, and the distance between measurement points shall be 0.5 to 2.0 meters. The number of dust particles with a particle size greater than or equal to 0.5 microns is allowed to exceed one point. The measurement points of the horizontal laminar clean room are only arranged in the first clean working area.

• For the turbulent clean room, 5 measurement points can be arranged according to the clean area less than or equal to 50 square meters. For every additional 20-50 square meters, 3-5 measurement points are added.

• Data collation

(1) The data collation of each measurement point should be carried out under the condition of stable operation of the test instrument. The average value is taken as the actual measured value of the point.

(2) For the determination of the number of dust particles greater than or equal to 0.5 microns: the maximum value of each measurement point is taken for the laminar clean room, and the average value of each measurement point is taken for the turbulent clean room.