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Material purification in the clean area
2025/7/16
Some objects only need one purification, while others require a second one. One-time purification does not require the purification of the indoor environment and can be set up in non-clean areas. Secondary purification requires a certain level of cleanliness in the room as well, so it is advisable to be located in the clean area or adjacent to it.
The material routes and personnel routes should be separated as much as possible. If materials and personnel can only enter the clean workshop from the same place, they must also enter through separate doors, and the materials must first undergo rough purification treatment. For situations where the production flow is not strong, an intermediate warehouse can be set up in the middle of the material route. If the production flow is very strong, a straight-through material route should be adopted.
Specifically, the "object purification" on the plane includes the following parts, namely packet unpacking, transfer and transmission.
1. Unpacking
The unpacking room can be divided into unpacking of outer packaging and unpacking of inner packaging.
The unpacking room is the largest source of pollution because it will shake off a lot of particles. Therefore, it should be located outside the clean room. The unpacking room should be equipped with a dust collection device, and the exhaust port of the dust collection device should be fitted with a super-clean filter bag. Only exhaust air is provided indoors, or there are both purification supply air and disinfection measures and exhaust air, but negative pressure or zero pressure should be maintained in the clean area in all cases. If the risk of pollution is high, negative pressure should also be maintained in the direction of the inlet.
The inner bag removal room is usually located in the clean area. It should be equipped with purified supply air and maintain negative pressure in the clean area. Sometimes, ultraviolet lamps can also be installed for disinfection.
2. Transmission
Transfer mainly refers to the brief and discontinuous transfer of objects between clean rooms.
The transfer mainly relies on the transfer window. The transfer window is a box with doors on both sides installed on the interior wall and can be placed on the floor. The air exchange caused by its switch is shown in the figure.
When the left window or door is opened, up to half of the air in the room is replaced by that in the right room. When the left door is closed and the right door is opened, another half of the air in the window is replaced by that in the right room, which means that an equivalent of one quarter of the air in the left room is replaced by that in the right room. This air volume is approximately only 0.125 cubic meters. Using the same calculation method as the buffer room, if the dust concentration in the clean room on the right is 10 times higher than that on the left, that is, the cleanliness level is 1 grade lower, then due to the moment of opening and closing the transfer window, the dust concentration in the left room (assumed to be 25 cubic meters) will increase by 1.005 times. This is truly negligible.
Transfer Windows are classified into general type, interlocking type and purification type according to their construction principles. The interlocking type is further divided into mechanical interlocking and electronic interlocking, and both can be equipped with ultraviolet lamps inside.
If the goods being transferred between the two rooms are not of different species and there is no cross-contamination, then a general type of transfer window can be used. It is of course better to use an interlocking type when conditions permit, but a non-interlocking one is definitely not impossible. Because other measures can be taken, such as "software" and education, to enable workers to master the correct usage method, that is, if the other party's window and door are not managed, one's own window and door should not be opened. Warnings can be given through signs, lights, etc.
If there is a possibility of severe cross-contamination during transfer, a purifying transfer window can be used. This type of transfer window has a purifying air circulation and maintains a relative negative pressure on the side being transferred.
3. Transmission
Transmission mainly refers to the long-term continuous movement of materials and objects between clean rooms.
The transmission mainly relies on conveyor belts and material elevators. The GMP regulations on this matter are shown in the table below. The pollution or cross-contamination caused by conveyor belts mainly comes from the long-term "dust and bacteria accumulation" of the conveyor belts and the air pollution caused by the air they carry.
The GMO regulations of the WHO regarding conveyor belts are much more lenient. Only conveyor belts of grade 100 that cannot be continuously disinfected are not allowed to pass through. It can be seen that this focuses on preventing the contamination caused by the "dust and bacteria" on the conveyor belt. As long as the conveyor belt is disinfected, there will be no restrictions.
According to the regulations of GMP in our country, materials to 10,000-level (generally for the production of sterile drugs) clean rooms can only be conveyed by segmented conveyor belts. Because in a 10,000-level environment, there are often local 100-level environments. But this meaning has not been made clear. This regulation is stricter than that of the WHO. To achieve this kind of transmission, the conveyor belt must be divided into sections at the opening, and the objects on one side of the conveyor belt are transferred to the other side by means of "relay turntables" and the like in various countries.
It is even more specific to emphasize that only the conveyor belts of 10,000-level biological cleanrooms with strong and live toxins and 10,000-level cleanrooms with strong allergenicity cannot pass through lower-level areas. Similarly, in this 10,000-level environment, there are also often local 100-level ones. In addition, there is a requirement for directional air flow at the transmission opening. This is in line with the spirit of dynamic isolation. No specific figure was provided for the velocity of the directional airflow, but as mentioned earlier, in accordance with conventional and ISO regulations, it can be taken as 0.2m/s. That is to say, for rooms with normally open openings, it is unrealistic to require the pressure difference between them to meet the standard. It is only necessary to ensure the speed of the opening. At this time, the flow through the opening may also be relatively large depending on the size of the opening.
If a room with a hole is connected by both a door and a corridor, but the main purpose of this room is to prevent contamination from adjacent rooms passing through the hole, while the contamination of the corridor is secondary, then it is only necessary to maintain the speed of the hole. There is no need to require a pressure difference that meets the standard between this room and the corridor.
If it is also required that this room maintain a sufficient pressure difference with the corridor (or other rooms), other measures must be taken, such as:
Minimize the area of the opening as much as possible, or cover it with a curtain to minimize the air volume needed to maintain positive pressure on one side, or increase the positive pressure on one side under the original air volume.
When necessary, a vertical air supply pipe should be set up on the side where the high pressure of the opening is transmitted, as shown in the figure, to form an air curtain to seal the opening.
If the materials are transported by elevator, to reduce cross-contamination, the following three points should be achieved:
People and objects cannot share one elevator.
Elevators should be located in non-clean areas.
If the elevator can only be located in the clean area, there should be a buffer room at the elevator entrance. "Elevators should not be located in clean areas. If they must be set up, a buffer room should be provided before the elevator." This regulation applies to both "material elevators" and "human elevators".
