Negative pressure weighing room comprehensive maintenance (GMP compliant version, easy to understand and implement)
1. Daily inspection (must be done every shift / every day)
Appearance and cleanliness
No dust or accumulated materials on the inner walls, workbench, return air filter, operation port; wipe with dust-free cloth + purified water / 75% ethanol, prohibit corrosion of the cabinet by strong acids and strong alkalis.
Parameter confirmation
Check the pressure difference gauge: the indoor negative pressure is stable at **-15~-30Pa**;
Check the wind speed: the vertical wind speed at the working surface is 0.35~0.45m/s;
The fan, lighting, and alarm functions are normal, without abnormal sounds or air leakage.
Operation norms
Do not knock on the HEPA high-efficiency filter, do not stack materials at the air outlet; start self-cleaning for 10~15 minutes before feeding and weighing.
2. Weekly maintenance
Deep cleaning: disassemble and wash the primary filter and return air filter (wash and dry with water, strictly prohibit sun exposure);
Check the cabinet sealing: no cracks or air leakage at the door frame, maintenance port, and glass rubber strip;
Calibrate pressure difference and wind speed sensors, record the ledger.
3. Monthly maintenance
Check the dust accumulation of the medium-efficiency filter, if the pressure difference increases, predict and replace in time;
Clean the fan cavity and internal air duct, remove accumulated dust;
Check the circuit, wiring, and start/stop switch, prevent poor contact;
Overall disinfection: ozone / ultraviolet + surface wiping combined disinfection (note that ultraviolet must not shine on people or materials).
4. Quarterly / Annual Key Maintenance (Core consumables)
1. Filter replacement (most important)
Primary filter: 1~3 months / water washing for reuse, 3~6 months mandatory replacement;
Medium-efficiency filter: 6~12 months, or replace immediately if the pressure difference exceeds the initial value by 2 times;
HEPA high-efficiency filter:
Regularly 1~2 years replacement; if high-toxicity / high-activity dust, shorten to 6~12 months;
After replacement, must do: leak detection (PAO leak detection) + wind speed calibration + pressure difference re-measurement, keep GMP verification records.
2. Fan and power part
Every year check the fan bearings, belt tightness, add lubrication; adjust the variable frequency parameters in time when the air volume decreases.
3. Seal and structure
Every year check the weld seams, tempered glass, and sealing strips of the cabinet, replace directly if aging and hardening, to prevent negative pressure leakage and dust leakage.
5. Prohibit illegal operation & Fault emergency
❌ Prohibit starting and removing the filter, prohibit blocking the return air outlet, prohibit long-term opening operation;
❌ HEPA filter must not be washed with water, knocked, or wiped;
In case of insufficient negative pressure / wind speed alarm: immediately stop feeding, seal the materials, stop the machine to check air leakage + filter blockage;
If a large amount of dust spills out: stop the machine for disinfection, detect the surrounding environment dust, and investigate filter damage.
6. GMP Required Ledger (must be checked during acceptance)
Daily operation record sheet (pressure difference, wind speed, cleaning records);
Filter cleaning / replacement records, PAO leak detection report;
Calibration certificate, maintenance work order, fault handling record.