How to judge the cleaning effect of the horizontal flow workbench filter after cleaning?

The horizontal flow workbench is a device that provides a local clean environment and is widely used in biological laboratories, electronic manufacturing, pharmaceutical production, and other fields. Daily maintenance is crucial for ensuring its cleanliness, operational stability, and extending its service life. The following are the key points for the daily maintenance of the horizontal flow workbench:
I. Daily maintenance
Check before startup
Check the surface of the workbench for any debris or stains and clean them up in time (75% alcohol can be used to wipe).
Check whether the appearance of the fan and filter is intact, and whether there is any damage or looseness.
Confirm that the power connection is normal and the switch function is intact.
Observation during operation
After starting up, observe whether the fan operates smoothly and if there are any abnormal noises or vibrations.
Check whether the indicator lights and the display on the control panel are normal, and whether the wind speed is within the set range (generally, the wind speed requirement for a horizontal flow workbench is 0.3 to 0.6m/s).
During operation, avoid placing items near the air outlet or return air outlet to prevent blocking the airflow.
Clean after use
Before closing the workbench, wipe the workbench surface, inner walls, and operating Windows with 75% alcohol or a special disinfectant to remove residual contaminants.
Clear the waste generated during the operation process to ensure that there are no leftover items on the workbench.
Turn off the power and record the operating conditions (such as abnormal noise, abnormal wind speed, etc.).
Ii. Weekly maintenance
Appearance and structural inspection
Clean the external surface of the workbench, including the sides, top, and bottom, to remove dust and stains.
Check the sealing performance of the workbench, such as whether the sealing strip of the operation window is intact, without aging or falling off, to ensure that no external contamination seeps in.
Check if the screws and connecting parts are loose and tighten them in time.
Preliminary inspection of the filter
Observe whether the surface of the pre-filter (primary filter) has accumulated too much dust. If it is dirty, remove it in time and clean it by blowing it back with compressed air (Note: The primary filter must not be washed with water).
Record the cleaning frequency and status of the pre-filter to provide a basis for subsequent replacement.
Fan performance inspection
Measure the wind speed at different positions on the workbench with an anemometer to ensure uniformity and compliance. If the wind speed drops significantly (below 0.3m/s), it is necessary to check for filter blockage or fan failure.
Iii. Monthly maintenance
Status assessment of high-efficiency filters
High-efficiency filters are the core for ensuring cleanliness. Every month, the cleanliness inside the workbench needs to be tested by a "dust particle counter" (usually required to reach a cleanliness level of 100 or 1,000). If the number of particles exceeds the standard, it may be that the high-efficiency filter is leaking or has failed.
Check whether the frame seal of the high-efficiency filter is intact, without any damage or deformation. If leakage is found, it should be replaced or resealed in time.
Electrical system inspection
Check if the power cord, plug, and socket are damaged or aged to avoid the risk of a short circuit.
Clean the control panel and switches to prevent dust accumulation from affecting operation.
Internal airflow detection
Use the smoke test method (such as a smoke-emitting pen) to observe whether the airflow direction inside the workbench is uniform and free of vortices, ensuring that the horizontal airflow covers the entire operation area without any airflow dead corners.
4. Regularly replace consumables
Primary filter: Depending on the usage frequency and environmental cleanliness, it is generally replaced every 1 to 3 months (if it still accumulates a lot of dust after weekly cleaning, it needs to be replaced in advance).
High-efficiency filters: Their service life is typically 1 to 2 years (or cumulative operation time reaches 1500 to 3000 hours). If the cleanliness test fails to meet the standards or they are damaged, they need to be replaced immediately (after replacement, the cleanliness should be retested to ensure it is qualified).
When replacing the filter, it is necessary to strictly follow the operating procedures to avoid contaminating the filter and the interior of the workbench.
V. Long-term Shutdown Maintenance
If the workbench is not used for a long time (more than one month), it is necessary to thoroughly clean the inside and outside first, remove the pre-filter, and store it in a sealed container.
Cut off the power supply and cover the workbench with a dust cover to prevent dust from entering.
Before reactivation, a comprehensive inspection of the equipment status is required, the primary filter should be replaced, and the cleanliness should be tested after running for 30 minutes. Only after passing the test can it be used.
Vi. Precautions
During the maintenance process, clean gloves and masks must be worn to avoid human contamination.
The replacement of high-efficiency filters must be carried out by professionals to ensure correct installation and prevent leakage.
All maintenance records should be archived in detail (such as cleaning time, filter replacement date, test data, etc.) to facilitate traceability and equipment management.
If any equipment malfunction is found (such as the fan not rotating, abnormal wind speed, or the cleanliness not meeting the standard, etc.), do not disassemble it by yourself. Instead, contact professional maintenance personnel for handling.
Through the above daily maintenance, the clean environment and stable operation of the horizontal flow workbench can be effectively guaranteed, and the risk of contamination during experiments or production processes can be reduced.
How to clean the filter of a horizontal flow workbench?
The filters of the horizontal flow workbench are divided into primary filters (pre-filters) and high-efficiency filters (HEPA/ULPA). The cleaning methods of the two are quite different and must be strictly distinguished and treated to avoid a decrease in filtration efficiency or equipment damage due to improper cleaning. The following are the specific cleaning methods and precautions
I. Cleaning of the primary filter (pre-filter)
The function of the primary filter is to intercept large particles of dust, hair, etc., protecting the subsequent high-efficiency filter. It can be cleaned regularly and reused. The specific steps are as follows:
Cleaning frequency
Depending on the cleanliness of the usage environment and the frequency of the workbench's use, it is usually cleaned once every 1 to 2 weeks. If there is a lot of dust in the environment (such as near construction areas or poorly ventilated areas), it can be shortened to once every 3 to 5 days.
Cleaning steps
Shutdown and disassembly: Turn off the power supply of the workbench, open the inspection panel of the pre-filter (usually located at the air inlet of the fan), and carefully remove the filter (note to record the installation direction to avoid reverse installation).
Compressed air cleaning: Blow compressed air at 0.2 to 0.3MPa in the opposite direction from the air outlet side to the air inlet side of the filter (i.e., from the clean side to the dirty side) to remove the dust adhering to the surface. When operating, keep a distance of 15 to 20cm from the filter to avoid excessive pressure damaging the filter material.
Secondary cleaning (optional): If there are still obvious stains after the compressed air cleaning, the filter can be gently rinsed in clean water below 40℃ (only applicable to cotton or synthetic fiber primary filters). Do not use detergents, hot water, or rubbing to avoid damaging the filter material structure.
Drying and resetting: After cleaning, place the filter in a cool area to dry naturally (do not expose it to direct sunlight or baking). Once it is completely dry, reinstall it in the original direction and tighten the screws on the inspection panel.
Precautions
If the filter is damaged, the filter material falls off, or it is still obviously clogged after multiple cleanings (manifested as a decrease in wind speed), a new primary filter must be replaced directly, and it cannot be used any longer.
During the cleaning process, avoid touching the surface of the filter material directly with your hands to prevent oil contamination.
Ii. Misunderstandings about the "Cleaning" of High-Efficiency Filters (HEPA/ULPA)
High-efficiency filters are the core components for intercepting particles smaller than 0.3μm. Cleaning is strictly prohibited for the following reasons:
The filter material of high-efficiency filters is superfine glass fiber or PTFE membrane, which is precisely structured and fragile. Any cleaning (such as blowing, wiping, or water washing) will damage the fiber structure of the filter material or the sealant, resulting in a sudden drop in filtration efficiency or leakage.
The clogging of high-efficiency filters is irreversible. Excessive dust accumulation can lead to a decrease in wind speed and excessive cleanliness. At this point, direct replacement is required instead of cleaning.
Iii. Maintenance and Replacement Tips for High-Efficiency Filters
Status monitoring
Regularly test the cleanliness inside the workbench with a dust particle counter or monitor the wind speed with an anemometer (if the wind speed is lower than 0.3m/s and the primary filter has been cleaned or replaced, it may be that the high-efficiency filter is clogged).
Replacement cycle
The typical service life is 1 to 2 years (with a cumulative operation of 1,500 to 3,000 hours), depending on the cleanliness of the environment and the frequency of use.
Replacement requirements
It must be operated by professionals. Before replacement, the interior of the workbench needs to be disinfected. When installing a new filter, ensure that the frame is tightly sealed (sealant can be applied for assistance). After replacement, the cleanliness needs to be rechecked. Only after passing the recheck can it be used.
Summary
Primary filter: It can be regularly blown back with compressed air or lightly rinsed with cold water (depending on the material). Replace it if it is damaged.
High-efficiency filter: Cleaning is prohibited. Only replace when it fails or leaks. Performance verification is required after replacement.

Proper maintenance of the filter is the key to ensuring the cleanliness of the horizontal flow workbench and avoiding the risk of equipment failure or contamination due to incorrect operation.
How to judge the cleaning effect of the horizontal flow workbench filter after cleaning?
The effect judgment of the horizontal flow workbench filter (mainly for the cleanable primary filter) after cleaning should be comprehensively evaluated by combining the appearance, equipment operation parameters, and actual cleanliness performance to ensure that it can effectively play the pre-filtering role, protect the subsequent high-efficiency filters, and maintain the normal operation of the workbench. The following are the specific judgment methods:
I. Judgment of the Cleaning Effect of the Primary Filter
Visual inspection
After cleaning, observe that there is no obvious visible dust, fibers, or stains on the surface of the filter. The filter material should not be damaged, deformed, or have fiber shedding. (If there are stubborn local stains but they are not damaged, it is acceptable.) If there is any damage, it will be directly determined that the cleaning is ineffective and replacement is required.
Check the fluffiness and air permeability of the filter material: If the filter material becomes compacted or hardened due to improper cleaning (such as excessive rubbing or high-temperature baking), it will lead to a decrease in air permeability. Even if the surface is clean, it is judged that the cleaning is ineffective.
Wind speed recovery test
Before cleaning, record the average wind speed on the workbench surface (if the wind speed drops to 0.25m/s due to filter blockage before cleaning).
Install the cleaned primary filter, start the machine, and run it for 30 minutes (to stabilize the airflow). Use an anemometer to measure the wind speed at different positions on the workbench surface (such as left, middle, and right points), and calculate the average value.
Qualification standard: The wind speed after cleaning should be restored to the normal range of the equipment (0.3 to 0.6m/s), and the difference from the wind speed in the "unclogged state" before cleaning should not exceed 10% (for example, if the normal wind speed is 0.45m/s, it should be ≥0.4m/s after cleaning). If the wind speed does not rise significantly, it indicates that the filter is still clogged (possibly due to deep dust not being removed), and it needs to be re-cleaned or replaced.
Resistance test (applicable to professional maintenance)
Measure the pressure difference (resistance) before and after the primary filter using a "differential pressure gauge." Before cleaning, the resistance will increase due to dust accumulation. After cleaning, the resistance should drop significantly, approaching the initial resistance value of a new filter (typically, the initial resistance of a primary filter is 5 to 10Pa. If the resistance remains higher than 30% of the initial value after cleaning, the cleaning effect is poor.
Ii. Indirect Verification: Combining high-efficiency filters with the cleanliness of the workbench
The core purpose of cleaning the primary filter is to reduce the load on the high-efficiency filter. Therefore, the following indirect indicators can be used to assist in the judgment:
The resistance change at the front end of the high-efficiency filter
If the primary filter is cleaned effectively, the resistance increase rate of the high-efficiency filter will slow down (this can be compared through long-term records: for example, if the resistance of the high-efficiency filter rises by 2Pa per week before cleaning and drops to 0.5 to 1Pa per week after cleaning, it indicates that the primary filter has regained its pre-filtering capacity).
Random inspection of the cleanliness inside the workbench
After cleaning the primary filter and running the workbench for one hour, use a dust particle counter to detect the particle concentration in the working area (for example, for a Class 100 cleanliness requirement, the number of particles ≥0.5μm should be ≤3520 /m³). If the cleanliness meets the standard and shows no significant difference (or is better) compared to before cleaning, it indicates that the cleaning of the primary filter has not affected the overall filtration system, indirectly proving the effectiveness of the cleaning.
Iii. Nonconformity Situations and Handling
If the following problems still exist in the primary filter after cleaning, it is determined that the cleaning is ineffective, and it needs to be replaced directly.
The appearance is damaged, the filter material has fallen off, or is deformed.
The wind speed has not returned to the normal range (below 0.3m/s).
After multiple cleanings, the resistance remains high, or the wind speed drops significantly again within a short period after cleaning (such as 1 to 2 days).
Summary
The core criterion for judging the cleaning effect of the primary filter is: there is no obvious pollution or damage to the appearance, the air velocity returns to the normal range, and the filtration efficiency of the equipment can be stably maintained. If only the surface is clean but the wind speed has not risen, it indicates that the cleaning has not solved the problem of deep blockage. A new filter needs to be replaced to avoid the premature scrapping of the high-efficiency filter due to the failure of the primary filter.