How should the air shower time of the air shower transfer window be set?

The setting of the air shower time for the air shower transfer window should comprehensively consider factors such as the type of items, contamination risk, and the grade of the clean room. A reasonable time setting can not only ensure the purification effect but also avoid resource waste. The following are the specific setting principles, methods, and precautions:
I. Setting Principles: Based on the balance between risk and efficiency
The area of the item list and the degree of contamination
The larger the surface area (such as large equipment, pallets) or the higher the risk of contamination (such as items transferred from non-clean areas), the longer the required air shower time.
For example, the shower time for small tools (such as tweezers) can be set at 10 to 15 seconds, while for large equipment, it may take 30 to 60 seconds.
Cleanroom grade requirements
High-grade cleanrooms (such as ISO Grade 5, corresponding to Class 100) need to strictly control contamination, and the air shower time should be extended to 20-40 seconds.
Low-grade cleanrooms (such as ISO 8, corresponding to Class 100,000) can be appropriately shortened to 10 to 20 seconds.
Airflow velocity and nozzle layout
If the wind speed is relatively high (such as 25m/s) or a double-sided air shower is adopted, the time can be shortened. Conversely, for single-sided air showers with lower wind speeds, the time needs to be extended.
Industry standards and process requirements
The pharmaceutical industry (such as the production of sterile preparations) usually requires a blow-off time of ≥30 seconds.
In the electronics industry (precision component transfer), 15 to 30 seconds can be set according to the particle control requirements.
Ii. Setting Methods and Steps
1. Initial parameter setting (equipment debugging stage
Default time: The factory default time for most devices is 15 to 20 seconds, which needs to be adjusted according to the actual scenario.
Test method:
The number of particles on the surface of the items before and after the air shower was detected by using a dust particle counter, and the purification efficiency at different times was recorded.
Example: If the number of particles drops by 90% after 15 seconds and by 99% after 30 seconds, then for high-risk scenarios, 30 seconds should be selected.
2. Dynamic Adjustment (Operation Stage)
Regular verification: Every quarter or after a major equipment overhaul, confirm whether the time is reasonable through the following methods:
Visual inspection: Observe whether there is any obvious dust residue on the surface of the item (such as the reflection of transparent packaging).
Microbial testing (pharmaceutical scenario): Take samples from the surface of the items after air rinsing to detect whether the colony count meets the standard.
Special scene processing:
When passing dust-generating items (such as plastic parts), temporarily extend the time by 10 to 20 seconds.
When continuously passing the same type of items, the interval time can be shortened (for example, adjusted from 20 seconds to 15 seconds) to improve efficiency.
3. Examples of control interface operations
The interfaces of devices from different brands may vary, but the basic logic is consistent:
Press the "Settings" key to enter the time adjustment mode;
Increase or decrease the time (unit: seconds) by pressing the "+" and "-" keys, usually within the range of 10 to 99 seconds.
Save the Settings and conduct a trial run to observe whether the double-door interlock and the air shower process are normal.
Iii. Common Problems and Solutions
Possible causes of the problem and solutions
The air shower time cannot be modified. The control program is locked or the keys are faulty. Check the operation permission (whether a password needs to be entered). Contact after-sales service for repair.
After the time is set, it will automatically restore the default motherboard. If the battery power is insufficient or there is a program error, replace the battery or reset the system parameters.
Poor air shower effect (excessive particles), too short time, decreased air velocity or prolonged filter blockage, test air velocity (standard value 20-25m/s), replace the filter.
If the interlock logic of the side door in the clean area is unlocked in advance or the sensor accidentally touches the calibration door magnetic switch, clean the dust on the surface of the sensor.
Iv. Industry Norms and Best Practices
GMP (Good Manufacturing Practice for Pharmaceuticals) requirements:
The transfer window in the aseptic production area should be set with "sufficient" blow-off time and undergo regular cleaning verification (such as once every six months).
ISO 14644-1 Cleanroom Standard
It is recommended to determine the minimum air shower time based on the particulate matter concentration attenuation curve (such as the logarithmic decrease law) to ensure that the number of residual particles is lower than the allowable concentration in the clean room.
Energy conservation optimization
For light and small items with high-frequency transmission, a "segmented air shower" mode (such as 30 seconds for the first time and 15 seconds for the subsequent time) can be adopted to reduce energy consumption.
V. Precautions
Prohibit arbitrary shortening of time: Even in low-risk scenarios, it is necessary to ensure a basic air shower of ≥10 seconds to avoid formalization.
Personnel training: Operating staff needs to be familiar with the time-setting rules for different items to avoid contamination caused by misoperation.
Recording and traceability: In compliance scenarios such as GMP, it is necessary to record the reasons, dates, and validation results of each time adjustment, and file them for future reference.
By scientifically setting the air shower time, not only can the environmental safety of the clean room be ensured, but also the material transfer efficiency can be optimized. It is one of the core links in the management of the clean area.