What Is a Pass Box?
A pass box is a device installed between two rooms of different cleanliness classes, such as a clean room.
It is used to transfer goods and equipment between the outside and the clean room and is used to prevent the introduction of particulates, bacteria, fungi, and other substances into the clean room that could cause product or operation failure or contamination.
Pass boxes make it easier and less contaminated to bring items in and out of two rooms of different cleanliness classes. They do so without the need for a human being to move in and out of the two rooms. It is also cost-effective because labor costs are not cut by changing clothes, etc. Since pass boxes are part of the facility, they are installed during the construction or expansion of a factory.
Uses of Pass Boxes
Pass boxes are used in manufacturing plants and research institutes that have rooms of different cleanliness classes.
They are used in a wide range of fields, including the manufacture of semiconductors, LCDs, electronic components, printing, precision instruments, and other products where the quality of the product depends on the presence of particulate matter, as well as in pharmaceutical plants, sterile treatment rooms, culture and other places where microbial contamination is a concern.
There are various types of pass boxes on the market, including standard, shower, and conveyor types, and selecting the appropriate type for the intended use and operating environment will lead to more efficient operations.
Principle of Pass Boxes
There are several types of pass boxes, including the standard type with only two doors, the shower type with an air shower inside, and the automatic type with a conveyor.
Pass boxes also have an airlock function to protect the clean room from contamination.
Other Information on Pass Boxes
1. Types of Pass Boxes
Standard Type
Standard pass boxes have a simple structure with two doors on each side. Many of them have an interlock function to prevent the opening of the other door when one side is open. By releasing the doors on both sides, contamination is prevented from being brought in directly from a room with a low cleanliness level.
Shower-type Pass Box
In a shower-type pass box, an air shower blows jets of air from the surrounding area when objects are placed inside the pass boxes. This is done to blow away surface particulates and bacteria and prevent them from moving while still attached.
The air is supplied and purified by a HEPA filter. However, since air showers can only blow air onto surfaces, they are not effective in areas where objects overlap each other and are not a panacea.
Automatic Pass Boxes
Forklifts are commonly used to transport goods in factories. When manufacturing precision equipment or pharmaceuticals in a clean room, conveyor-type pass boxes are installed to carry on whole pallets. Conveyor-type pass boxes are also equipped with an air shower to prevent the introduction of particulate matter from the outside.
Circulation-type Pass Boxes
Other types of pass boxes are also available that circulate normal air through the pass boxes to prevent contamination of the interior and to clean the goods and materials to be delivered.
2. How to use Pass Boxes
When manufacturing quality products, people and objects can cause dust and bacterial contamination. The use of pass boxes eliminates the effects of particulate matter from clothing and prevents the attachment of particulate matter and bacteria. It also reduces the movement of people across the cleanliness area and allows only objects to be brought in. In this way, a clean environment is maintained in the clean room.
Specific instructions for use are as follows:
Open the door on the opposite side of the clean room and wipe the inside of the pass boxes using ethanol or other liquids. The cleaning method varies depending on the application, but if the items to be moved can also be cleaned and placed in the pass boxes, they are placed in the pass boxes.
If the pass boxes are equipped with a UV irradiation function, the UV lamp will automatically turn on for a set period after the door is closed to perform UV sterilization. If the pass boxes are equipped with an air shower, after closing the door, jet air is blown to remove dust from the outer surface.
After a certain period has elapsed after the jet air has finished blowing, the other door is opened and the items are taken into the clean room after the blown dust has settled.
3. A Glove Box with Pass Boxes
Glove boxes are used when handling substances or germs that are dangerous to handle directly, such as when handling air-sensitive materials or when working under chemically inert conditions.
Some glove boxes are circulated by an external pump, while others can be connected to a vacuum pump. Some glove boxes are equipped with pass boxes. The pass boxes minimize the amount of outside air carried into the glove box.