Replacement Frequency of High-Efficiency Filters (HEPA/ULPA)
The replacement frequency of high-efficiency filters (HEPA/ULPA) mainly depends on "resistance change, operating environment, and cleanroom classification". The recommended replacement cycle is 6–18 months for general scenarios, and shortened to 3–6 months for heavily polluted or high-cleanliness grade environments. Specific criteria are as follows:
1. Core Criterion: Replace When Resistance Meets the Threshold
This is the most scientific and rigid indicator, directly related to the actual load of the filter.
Initial resistance: The standard initial resistance of high-efficiency filters is 150–250Pa (under rated air volume).
Replacement threshold: Must replace when the operating resistance reaches twice the initial resistance or exceeds 350–400Pa.
Practical suggestion: Monitor in real time through the differential pressure gauge of the cleanroom HVAC system, and replace promptly when the value meets the standard to avoid reduced air volume, increased energy consumption, or filtration failure.
2. General Replacement Cycles by Application Scenarios
The concentration of pollutants varies greatly in different environments, so the cycle needs to be adjusted flexibly:
High-cleanliness grade scenarios (ISO Class 5 and above, e.g., semiconductor factories, pharmaceutical sterile areas): 3–6 months.
Regular clean scenarios (ISO Class 6–8, e.g., electronic assembly workshops, food processing cleanrooms): 6–12 months.
Ordinary commercial/industrial scenarios (e.g., office building fresh air systems, general hospital wards): 12–18 months.
Heavily polluted scenarios (e.g., chemical workshops, industrial cleanrooms with high dust levels): 1–3 months, with frequent replacement of pre-installed primary/medium-efficiency filters.
3. Key Factors Affecting Replacement Frequency
Front-end filtration effect: Regular replacement of primary (G4) + medium-efficiency (F7/F8) filters (1–3 months for primary filters, 3–6 months for medium-efficiency filters) can significantly extend the service life of high-efficiency filters.
Air volume and operating time: Systems operating 24/7 with air volume close to the rated value have higher filter loads, requiring a 30%–50% shorter replacement cycle.
Pollutant type: Environments containing oil fumes, chemical vapors, or viscous dust can easily clog the filter, requiring more frequent replacements.
4. Special Cases: Immediate Replacement Signals
Replace immediately without waiting for the cycle or resistance threshold if:
The filter is damaged or leaking (failed PAO/DOP leak test).
The particle concentration in the cleanroom continues to exceed the standard, and filter failure is confirmed after eliminating other factors.
The system air volume drops significantly, affecting the stable differential pressure of the cleanroom.
