Does the high-efficiency filter of the horizontal flow workbench need to be replaced regularly?

The high-efficiency filters (HEPA/ULPA) of the horizontal flow workbench need to be replaced regularly, but the replacement cycle is not a fixed time point. Instead, it depends on the usage environment, operating status, and performance test results. The following is the core information about the replacement of high-efficiency filters:
I. Why is it necessary to replace High-efficiency filters?
High-efficiency filters are the core components for controlling the cleanliness of workbenches. Their filter materials (such as superfine glass fibers and PTFE membranes) filter out particles smaller than 0.3μm through physical interception. Once dust accumulates, its performance cannot be restored through cleaning.
After long-term use, the pores of the filter material will be clogged by dust, resulting in a decrease in the outlet air velocity and an excessive cleanliness of the working area (such as an increase in particle concentration).
If too much dust accumulates, it may also increase the load on the fan, leading to higher energy consumption of the equipment, increased noise, and even damage to the fan.
In extreme cases, the filter material or the sealing rubber of the frame may be damaged or leak due to aging and vibration, directly losing its filtering function and polluting the working environment.
Ii. Basis for Judging the Replacement Cycle (Key Indicators
The replacement of high-efficiency filters is not solely based on a fixed time. It should be comprehensively judged in combination with the following indicators:
The wind speed dropped to the critical value
During normal operation, the average wind speed on the horizontal flow workbench surface should be maintained at 0.3 to 0.6m/s (there may be slight differences depending on different standards).
If the wind speed remains below 0.3m/s even after the primary filter has been cleaned or replaced (and still cannot rise after adjusting the fan frequency), it indicates that the high-efficiency filter is severely clogged and needs to be replaced immediately.
The cleanliness test failed to meet the standard.
Regularly use a dust particle counter to detect the particle concentration in the working area (for example, for a class 100 workbench, the number of particles ≥0.5μm should be ≤3520 per m³).
If the standards are not met in two consecutive tests (with an interval of one week), and other factors such as clogging of the primary filter and poor equipment sealing are ruled out, it can be determined that the high-efficiency filter has failed and needs to be replaced.
Excessive resistance
The initial resistance of high-efficiency filters is usually 100 to 200Pa (with differences among different models). When the operating resistance reaches more than twice the initial resistance (for example, 200Pa initially, exceeding 400Pa or more), it indicates that the filter material is severely clogged and should be replaced.
Physical damage or leakage
If, through leak detection tests (such as the PAO smoke emission method), it is found that the filter frame is poorly sealed or the filter material is damaged (with leakage points), even if the usage time is short, it must be replaced immediately; otherwise, it will lead to contamination of the clean area.
Iii. Reference Replacement Cycle (Not Absolute Standard)
Under normal usage conditions (such as in moderately clean environments like laboratories and clean workshops, operating for 8 hours per day), the reference service life of high-efficiency filters is 1 to 2 years (with a cumulative operation of approximately 1,500 to 3,000 hours).
If the usage environment has a lot of dust (such as being close to outdoor air vents or production workshops), or if the workbench operates 24 hours a day, the replacement cycle may be shortened to 6 to 12 months.
If the environmental cleanliness is high (such as a cleanroom of Class 10,000 or above) and the usage frequency is low, it can be extended to 2 to 3 years, but the performance needs to be confirmed through regular testing.
Iv. Precautions for Replacement
Professional operation: It must be replaced by trained technicians to avoid poor sealing of the frame (leakage) due to improper installation.
Preparations before replacement: Before replacement, the interior of the workbench needs to be cleaned and disinfected to prevent dust from falling into the new filter.
Performance verification: After replacement, the cleanliness of the working area should be tested with a dust particle counter, and the leakage of the filter should be detected by the PAO smoke emission method. Only after passing the tests can it be put into use.
Record traceability: Each time the filter is replaced, information such as the filter model, replacement date, and test results should be recorded to establish a maintenance file.
Summary
The replacement of high-efficiency filters is a necessary maintenance step to ensure the performance of horizontal flow workbenches. It needs to be dynamically judged through indicators such as air velocity, resistance, and cleanliness, rather than simply being replaced according to time cycles. Regular inspection (recommended once every 3 to 6 months) is the key to determining the timing of replacement, avoiding the risk of contamination due to excessive use or cost waste caused by premature replacement.