Why are clean rooms not clean?

According to the classification of cleanliness levels in ISO14644-1, the cleanliness levels we usually use are Class 5, 6, 7, and 8, which are basically equivalent to Class A, B, C, and D specified in GMP.
Particle reference for judging whether the cleanliness is qualified: particles with a particle size greater than or equal to 5 microns (usually called large particles) and particles with a particle size greater than or equal to 0.5 microns (usually called small particles).

The cleanliness of a cleanroom is a dynamic balance formed by the combined effects of dust particle generation, purification capacity and the surrounding environment.

We will analyze the situation that the cleanliness is not up to standard from these three aspects

1.The amount of dust particles is too large

When there are a large number of dust-producing objects in the cleanroom, the purification ability of the air conditioner cannot quickly dilute the particles in the air, resulting in the cleanliness level exceeding the standard. There are three situations:

• There are crushers, tablet presses and other equipment with a large amount of dust in the room;
• The room is not hygienic and the cleaning is not thorough;
• Man-made pollution caused by poor control of personnel in the room, may be caused by too many personnel, insufficient cleanliness of clean clothes, and clean clothes are not in compliance with the regulations.

2.Insufficient purification capacity

The purification of the cleanroom completely depends on the clean air supply of the purification air-conditioning unit. When the clean air supply capacity is insufficient, the purification capacity of the cleanroom is also insufficient, resulting in an increase in the number of particles and excessive cleanliness. At this time, it is also divided into the following three situations:

• The air supply volume is insufficient and the number of air changes is not enough. The blockage of the primary, middle and high-efficiency filters results in a decrease in the air supply volume, a decrease in the frequency of the air supply unit, a decrease in the opening of the air supply valve, and a decrease in the fresh air volume;
• The leakage of the high-efficiency filter causes the clean air supply to be not clean enough;
• The air distribution in the room is unreasonable, resulting in local eddy currents and dead ends.

3.Surrounding environment impact

When the cleanliness of the surrounding adjacent rooms is relatively poor or even a low-level room, and the pressure difference between the room and the surrounding adjacent rooms is negative pressure, the air from the surrounding adjacent rooms enters the room, bringing in a large number of particles, causing The cleanliness exceeds the standard.

In the daily monitoring process, sometimes the quantity of one kind of particles is qualified but the other kind of particles is not qualified. According to our experience, we believe that the main reasons are as follows:(The possibility of ranking is in order)

Large particles are qualified, small particles exceed the standard:

• There is leakage in the high-efficiency filter;
• There is a dust source that produces a large number of small particles in the room.

Small particles are qualified, large particles exceed the standard：

• The sanitation of the room is not good and the cleaning is not thorough;
• Man-made pollution caused by poor control of personnel in the room;
• There is a dust source that produces a large number of large particles in the room.

When we find the cause of the cleanliness exceeding the standard, by solving the corresponding problems, the cleanroom will be restored to the design level and meet the requirements for use.