What is clean room? - Cleanroom definition
- 26, 02, 2021
1. What is a cleanroom?
Cleanroom is not just a room that is clean, but it has a special meaning and is defined by ISO standard as:
"It is a room in which the concentration of airborne particles is controlled,
and is constructed and used in such a way to minimise the introduction, generation,
and retention of airborne particles inside the room and in which other relevant
parameters, e.g. pressure, temperature and humidity are controlled as necessary."
The function of cleanroom is to minimise the introduction, generation and retention of particles, which is achieved by supplying large quantities of filtered air, personnel use clothing that minimize the dispersion of particles and the material used to built cleanroom do not generate any particle and can be easily cleaned.
Cleanroom can also control the temperature, humidity, sound, lighting, and vibration.
2. Types of cleanroom
Cleanrooms are classified into two major types based on their method of ventilation. These are
- Turbulent airflow cleanrooms
- Unidirectional airflow cleanrooms
Turbulent airflow cleanrooms are also known as "non-unidirectional". This type of airflow is generally used in offices, shops, etc. In this cleanroom, air is supplied by an air-conditioning plant through diffusers in the ceiling.
Unidirectional flow cleanrooms are also known as "laminar flow". The unidirectional cleanroom uses large amount of air than the turbulent airflow cleanroom. Because of the directed air movement, it minimizes the spread of contamination about the room and sweeps it out through the floor.
Image source: Spaceindustries UK
Fig.1 shows a turbulently ventilated cleanroom receiving clean air through air diffusers in the ceiling. Clean air mixes with the room air and removes airborne contamination by extracting the air at the bottom of the walls. The air changes are normally >20 per hour, this being much greater than that used in ordinary rooms. In this type of cleanroom, the contamination generated by people and machinery is mixed and diluted with the filtered air and then removed.
Fig 2. shows a unidirectional flow cleanroom. In this cleanroom, HEPA filters are installed across a ceiling and supply filtered air. The air sweeps all the contaminants from the room in a unidirectional way and exits through the floor.
3. Cleanroom Classification
Based on the application, cleanrooms are classified into:
- Industrial Cleanroom
- Biological Cleanroom
Biological cleanroom functions like industrial cleanroom. Besides, it also needs to control contamination and the density of micro-organism.
Based on the cleanliness level, cleanrooms are classified into:
- U.S Federal Standard
- ISO 14644
U.S Federal Standard measured the class of cleanroom by the numbers of particles larger than than 0.5 micron in diameter contained in one cubi foot of air. For example, Class 100 cleanroom contains fewer than 100 off such particle on one cubic foot.
Beside U.S Federal Standard, ISO 14644 is another type of cleanroom classification.
Table 10.1 show the details of the two standards.
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