As a classification method for clean rooms, they are generally divided according to the shape of indoor airflow. According to this method, clean rooms can be roughly divided into the following three categories.
1. Vertical laminar flow type (downward flow method)
This is a method in which HEPA or ULPA filters are installed on the ceiling, from the top plate directly down to the ground, and can provide clean air to the clean room at the same speed. This equipment is large and expensive, but as a clean room, it is the best in terms of performance.
| summary | Features | |
| Air outlet, filter location | Ceiling (above 80) (Figure 3) | Advantages: ●It is not affected by the number of people working in the room or the working status, and can ensure a high degree of cleanliness ●Because of vertical laminar flow, the ventilation frequency is high, so a high level of cleanliness can be achieved in a short time ●There is almost no dust accumulation, and even if it is contaminated, it can be quickly restored Disadvantages: ●High equipment cost ●High operating cost ●It is difficult to protect the area of the clean room |
| Air inlet location | Sieve bar or perforated plate (Figure 3) | |
| Airflow state | Vertical laminar flow | |
| Ventilation frequency (airflow velocity) | 250-650 times/h0.25m/s left | |
| Temperature range | right | |
| Humidity range | 22℃ +1-3℃ | |
| Indoor and outdoor pressure difference | RH45% +5-10% | |
| Required mechanical room | -25Pa (0.5-2.5mmH20) | |
| Building interior materials | There are regulations | |
| Difficulty of the project | Requires a high level of technology | |
| Room size restrictions | No special requirements | |
| Room effective working area | Can get a large area | |
| Operability | Good | |
| Operation cost | High | |
| Management | Implement high-level management | |
2. Horizontal laminar flow type (cross flow method)
This is a method in which HEPA or ULPA filters are installed on the wall plate, and clean air is provided from the wall to the opposite wall at the same speed. Because it is a horizontal laminar flow, the cleanliness of the downstream side is lower than that of the upstream side of the airflow. However, compared with the vertical laminar flow method, it has the characteristics of smaller equipment and lower cost.
| summary | Features | |
| Blow-out port, filter location | On the wall on one side of the room (Figure 4) | Advantages ●Dust accumulation and re-liberation caused by eddy currents and dead corners ●The cleanliness of the room is not affected by the number of workers and the working status. Disadvantages ●A high level of cleanliness can be guaranteed in places close to the blowing layer, but the cleanliness will be reduced in places close to the suction layer. ●It is difficult to expand the clean room ●The equipment cost is not as high as the vertical type, but it is still expensive ●The improvement of the preparation room such as the cabinet, dressing room, air shower, etc. and ●Clean the work clothes should be paid full attention to, |
| Blow-in port location | The wall opposite the outlet (Figure 4) | |
| Airflow state | Although it is a horizontal laminar flow, the lower wind flow will gradually be polluted. | |
| Ventilation frequency (airflow velocity) | 30-650 times/H (0.45m/s | |
| Temperature range | 22℃ +1-3℃ | |
| Humidity range | RH45% +5-10% | |
| Indoor and outdoor pressure difference | -25Pa (0.5-2.5mmH20) | |
| Required mechanical room | Medium | |
| Building interior materials | There are considerable restrictions | |
| Difficulty of the process | Requires a slightly higher level of technology | |
| Room size limit | Restricted | |
| Effective working surface of the room | Restricted | |
| Operability | The movement of personnel is restricted | |
| Operation cost | Medium | |
| Management | Slightly requires a higher level of management | |
3. Non-laminar flow type (conventional type)
Compared with the above-mentioned laminar flow forms, its equipment cost is much lower, but due to the appearance of non-laminar flow parts, the indoor airflow is turbulent, and the microparticles float in the air, making it difficult to ensure high cleanliness. M3.5 (100) and M4.5 (1000) occasions
In the occasions where the cleanliness level is required to reach M3.5 and M4.5, most of them can reach the laminar flow type
| summary | Features | |
| Air outlet, filter location | Front end of air conditioning duct (Figure 5) | Advantages: ● Simple and easy filter and air treatment ● Cheap equipment cost ● Easy to expand ● High level of cleanliness can be achieved by using a clean bench Disadvantages ● Indoor cleanliness will change due to the operator ● Eddy current and turbulence are easy to generate, and polluted particles may circulate indoors ● Due to the small number of ventilation times, it takes a long time to achieve the required cleanliness, and the power cost is high ● Pay full attention to the completeness of rooms such as cabinets, dressing rooms, and air showers, and the cleaning of work clothes, etc. |
| Air inlet location | Side on the floor (Figure 5) | |
| Airflow state | Produce turbulence | |
| Ventilation frequency (airflow velocity | 20-50 times/h | |
| Temperature range | 22℃ +1-5℃ | |
| Humidity range | RH50%+10% | |
| Indoor and outdoor pressure difference | 25Pa(0.5-2.5mmH20l | |
| Required mechanical room | Some restrictions | |
| Building interior decoration materials | Some restrictions | |
| Difficulty of the project | No restrictions | |
| Indoor size restrictions | Restricted | |
| Effective working area of the room | No restrictions on human movement | |
| Operability | Low cost | |
| Operation cost | Slightly higher management level | |
| Management | Slightly requires a higher level of management | |
