How to count particles in a clean room

I. What is A Clean Room

A clean room, also known as a clean room, is an environmental facility that controls particles, temperature, 

humidity and other contaminants, and is widely used in industries such as Semiconductor, pharmaceutical and aerospace. It is designed to provide an extremely clean working environment to ensure product quality and reliability. The construction of a clean room involves a variety of engineering techniques, including air filtration, airflow design and material selection.

In a clean room, the level of particulate matter in the air can have a direct impact on the cleanliness of the manufacturing process. Common particles can be dust, microorganisms, chemical gases, etc. These contaminants can lead to product defects. Therefore, it is especially important to accurately monitor and control the particle count in a clean room. According to the ISO 14644-1 standard, the particle count level of a clean room is defined by a specific particle size and number.

In addition, the environmental control of the clean room also includes the monitoring and regulation of temperature and humidity, for example, the temperature is usually controlled at 20-24°C and the humidity is maintained between 30% and 60%. Through these strict control measures, the clean room can effectively reduce the number of particles to ensure the cleanliness of the production environment.

II，Clean room cleanliness level standards

The cleanliness level of the clean room is determined by the particle count test results. According to the ISO 14644-1 standard, clean rooms are divided into several classes, usually based on the maximum number of particles allowed per cubic meter of air. For example, ISO1 requires that no more than 10 particles of 0.1 microns per cubic meter of air be present, while ISO9 allows 20,000,000 particles of 0.5 microns per cubic meter of air.

Specifically, the following are particle count standards for several common cleanliness classes:

• ISO 5

  The number of 0.5 micron particles per cubic meter of air must not exceed 3,520.

• ISO 7

  The number of 0.5 micron particles per cubic meter of air shall not exceed 352,000.

• ISO 8

  The number of 0.5 micron particles per cubic meter of air shall not exceed 3,520,000.

These standards are not only applicable to the design and construction of cleanrooms, but also provide a standardized basis for the daily monitoring of cleanrooms. In order to ensure that the cleanroom meets these standards in the long term, regular testing and maintenance is necessary.

III, clean room particle count how to test

Particle count detection generally uses specialized instruments, such as laser particle counters. This equipment can monitor the number and size distribution of particles in the air in real time. By setting the particle size range, the instrument can provide a specific size of the particle counting data. For example, common size ranges include 0.1 micron, 0.5 micron, 1 micron and 5 micron.

The testing steps typically include the following:

1. Equipment Calibration

Prior to performing particle counting tests, the laser particle counter must be calibrated to ensure the accuracy of the data. The calibration process typically requires the use of standard particles for comparison to adjust the sensitivity of the equipment.

2. Sampling location and time

Choosing the appropriate sampling location and time is critical to ensure data representativeness. Personnel activities in the clean room should be avoided, and locations close to air inflow and outflow should be selected for testing. It is generally recommended that the duration of each test be 5-10 minutes to obtain stable data.

3. DATA ANALYSIS

After the test is completed, the collected particle count data needs to be analyzed. The following formula is usually used to calculate the particle count concentration:

C_n = {N}÷{V}

Where (C_n) is the particle concentration (particle count/m3), (N) is the total number of particles measured, and (V) is the volume of air detected (m3). Based on the different particle size ranges, the cleanliness level in compliance with the ISO standard can be further analyzed.

Through the above steps, cleanroom managers can keep track of the changes in particle concentration in the room in real time and adjust the operation status of the ventilation and filtration system in a timely manner, in order to ensure the continuous compliance of the cleanroom environment.