What is the application principle of the air shower transfer window?

The application principle of the air shower transfer window
The air shower transfer window is an air purification device used in clean rooms (such as laboratories, pharmaceutical factories, electronic workshops, etc.). Its main function is to reduce the entry of external contaminants into the clean area when transferring items, while also cleaning the surface of the items. The core principle is to purify the transferred items through high-speed clean air flow sweeping and air filtration systems.
I. Core Components and Structure
The air shower transfer window is usually composed of the following parts:
Box body: Sealed metal structure, separating the clean area from the non-clean area.
Double-door interlock system: Both sides of the door cannot be opened simultaneously to prevent cross-contamination.
Fan and nozzle: The built-in fan generates high-speed airflow, which is sprayed onto the surface of the item through the nozzle (usually made of stainless steel).
Filtration system: It includes primary filters and high-efficiency filters (HEPA or ULPA), which are used to filter dust particles in the air.
Control device: Controls the start and stop of the fan, the duration of the air shower (usually set at 10 to 60 seconds), and the interlock logic of the door.
Ii. Working Principle and Process
Item placement stage
Open the door on the side of the non-clean area, put the items into the transfer window, and close the door.
The double-door interlock system is activated to ensure that the side doors of the clean area cannot be opened.
Wind shower sweeping stage
The control system triggers the fan to start. The air is filtered through the primary filter and then pressurized by the fan and sent into the high-efficiency filter to form a clean airflow (the filtration efficiency for particles with a diameter of ≥0.3μm is ≥99.97%).
Clean air flow is sprayed onto the surface of items at a high speed of 20 to 25m/s through nozzles on both sides or the top. By taking advantage of the impact force and shearing force of the airflow, dust, hair, debris, and other contaminants adhering to the surface of the items are blown off.
During the air flow purging process, pollutants are drawn into the return air outlet at the bottom along with the airflow. After being re-filtered by the primary filter, they are recycled (some models are equipped with exhaust devices to expel the polluted air from the system).
The stage of picking up items in the clean area
After the set air shower time is over, the side door of the clean area is unlocked. Personnel take out items from the clean area and close the door to complete the transfer.
Iii. Key Technical Points
Airflow direction and nozzle layout
Nozzles are usually arranged at a 45° Angle to ensure that the airflow covers the entire surface of the item without any dead corners for blowing.
Common airflow patterns include single-sided air showers (suitable for light and small items) and double-sided/triple-sided air showers (suitable for large or irregular items).
Filtration efficiency and air volume design
High-efficiency filters are the core components and need to be inspected and replaced regularly (usually every 1 to 2 years depending on the usage frequency).
The air volume of the fan should match the volume of the transfer window to ensure sufficient air circulation times (generally ≥20 times per minute) to guarantee the purging effect.
Pressure control
Some high-end transfer Windows are equipped with differential pressure sensors to maintain an internal pressure slightly higher than that in non-clean areas, preventing unclean air from seeping in.
Iv. Application Scenarios and Advantages
It is widely used in places with high cleanliness requirements such as pharmaceutical, food, electronic, and biological laboratories to transfer reagents, tools, packaging materials, and other items.
Advantages:
It replaces the traditional manual wiping disinfection, which is more efficient and leaves no blind spots.
The double-door interlock design blocks the pollution path from both physical and airflow aspects.
It can be linked with the air conditioning system of the cleanroom to maintain the overall cleanliness level of the area.
V. Maintenance and Precautions
Clean the primary filter regularly (once a week) to prevent blockage and affect the air volume.
High-efficiency filters need to be tested by a dust particle counter and can only be used after meeting the standards.
The transfer of dust-generating or non-compliant items (such as paper documents, unsealed containers, etc.) is prohibited to prevent contamination of the internal system.
Based on the above principles, the air shower transfer window achieves "sterile transfer" between the clean room and the outside world, and it is an indispensable key equipment in modern clean engineering.