The core of daily maintenance for the negative pressure weighing chamber is as follows: daily cleaning + parameter inspection, weekly deep cleaning and seal check, monthly filter and duct maintenance, annual leak detection and calibration. The entire process follows GMP to ensure stable negative pressure, compliant airflow, and no cross-contamination.
1. Daily Maintenance (per shift / per day)
1. Before startup check
Negative pressure value: The differential pressure gauge shows **-15 to -30 Pa**, stable without fluctuations.
Working surface wind speed: 0.35 to 0.45 m/s, no turbulence.
Function status: Fan, lighting, alarm are normal, no abnormal noise, no air leakage.
Appearance cleanliness: Inner walls, tabletop, return air vents, operation ports have no dust or residual materials.
2. Cleaning and disinfection (must be done after operation)
Power off protection: Turn off power and ventilation, wear gloves, protective clothing, and mask.
Remove residues: Use dust-free tools to remove residual materials on the tabletop to avoid touching the materials.
Surface wiping: Dip a dust-free cloth in purified water / 75% ethanol, wipe the tabletop, side walls, and door body from top to bottom, from inside to outside in a single direction; use cotton swabs to clean the gaps.
Disinfection: Secondary wipe with 75% ethanol or 3% hydrogen peroxide, leave it to stand for 10 to 15 minutes.
Drying: Let it air dry or dry with a dust-free cloth, do not allow water to enter the electrical components and filters.
Prohibited: Do not use strong acids or strong alkalis; do not wash HEPA with water; do not stack materials at the return air vent.
3. Shutdown and record
Self-cleaning for 10 to 15 minutes after operation before shutting down.
Fill in operation, differential pressure, wind speed, cleaning records to ensure traceability.
2. Weekly Maintenance
Primary / return air filter: Remove for washing (soft brush + neutral cleaner), air-dry, avoid direct sunlight, reinstall and seal.
Seal check: No cracks or air leakage in door frames, inspection ports, and glass gaskets.
Parameter calibration: Calibrate and record the differential pressure and wind speed sensors.
Overall disinfection: Ozone / ultraviolet (unattended) + surface wiping; ultraviolet prohibited for people / materials.
3. Monthly Maintenance
Medium-efficiency filter: Check for dust accumulation, replace when differential pressure exceeds threshold.
Fan and duct: Clean the dust accumulation in the fan chamber, inner walls, and duct, prevent secondary dusting.
Circuit inspection: No looseness or overheating of wiring, switches, and frequency converters.
Gloves (Grade A): Clean, leak check, replace if damaged.
4. Quarterly / Annual Maintenance
Quarterly: Replace primary efficiency filter; check HEPA differential pressure (final resistance exceeds 500 Pa, replace).
Annual: HEPA leak detection; fan / control system calibration; comprehensive seal and airflow test.
5. Filter Replacement Cycle (Reference)
Primary efficiency: 1 to 3 months (replace when clogged).
Medium efficiency: 3 to 6 months (replace when differential pressure increases).
HEPA: 12 to 24 months (replace when differential pressure exceeds 500 Pa or leak detection fails).
6. Safety and Compliance Key Points
Power off for 10 minutes before operation to prevent electric shock.
Use GMP-approved cleaning agents / disinfectants, compatible materials.
Prohibit use of fiber cloths; tools are dedicated and divided.
Establish maintenance ledger: date, project, parameters, personnel, abnormal handling.
7. Common Abnormal Handling
Insufficient negative pressure (> -15 Pa): Check for door / seal leakage; primary / medium-efficiency blockage; abnormal fan speed.