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

I. General Standards (Pharmaceutical Factory / GMP mainstream) Normal operating conditions (ordinary raw materials and excipients, low dust): HEPA high-efficiency filter: 12-24 months High dust / high activity / toxic powders (anti-cancer drugs, hormones, sterile powders, fine powders of traditional Chinese medicine): HEPA high-efficiency filter: 6-12 months. Forced shortening II. Not based on time, but on pressure difference (most accurate, GMP recognizes this) Based on the initial pressure difference of the equipment: When the final pressure difference reaches twice the initial pressure difference / the upper limit of the manufacturer’s calibration → immediately replace, don’t wait for the cycle Daily pressure difference increase is fast: indicates a large dust load, replace in advance III. Reference period for matching filters (companion notes) Primary efficiency: 1-3 months of cleaning, 3-6 months of replacement Intermediate efficiency: 6-12 months of replacement (protecting the high-efficiency filter, frequent replacement of intermediate efficiency = prolonging the life of HEPA) IV. Key mandatory requirements (must be inspected by inspection agencies) After each replacement of the high-efficiency filter: must conduct PAO leak detection + wind speed balance test + re-calibration of pressure difference, and retain the verification report.

The core principle of the negative pressure weighing chamber is: through vertical unidirectional flow + local exhaust to form a stable negative pressure, locking dust / pollutants within the operation area and preventing them from leaking out, while ensuring the cleanliness of the operation area. I. Core Structure (Key Components of Air Flow Path) Primary / Intermediate Filter: Pre-filters large particles to protect the fan and the high-efficiency filter. Centrifugal Fan: Provides power to drive the air circulation and exhaust. High Efficiency Filter (HEPA): Captures particles of 0.3μm with a retention rate of ≥ 99.99%, ensuring the cleanliness of the supply air. Equalizing Mesh / Equalizing Membrane: Forms a uniform vertical laminar flow (about 0.45m/s). Return / Exhaust System: Collects the dust-containing air flow, partially recycles and partially discharges. Pressure Difference Control System: Maintains a relative negative pressure of the operation area to the external environment (usually -15~-30Pa). II. Operating Process (Air Flow and Negative Pressure Formation) Return Air Purification Dust-containing air in the operation area enters through the bottom return mesh, and passes through the primary / intermediate filters successively to remove large particles. Supply Air Purification The purified air is sent by the fan into the high-efficiency filter

Frequency of integrity testing for high-efficiency filters in the automatic double-door cargo washing room According to GMP, cleanroom acceptance standards and common industry practices, the frequency is divided into the following levels. You can directly follow and implement them: 1. Routine usage frequency (most commonly used) Test once every 6 months Applicable to: cargo washing rooms in electronic, food, and ordinary pharmaceutical cleanrooms. 2. High-purity clean environment Test once every 3 months Applicable to: sterile drugs, medical devices, biological laboratories, high-level cleanrooms (10,000-level / 10,000-level / 100-level). 3. Immediate testing situations (no fixed cycle) Test immediately if any of the following conditions are met: High-efficiency filter has just been replaced or installed The cargo washing room box or high-efficiency filter has been disassembled, moved, or collided Pressure difference is suddenly abnormal (too high / too low) The particle count in the clean area exceeds the standard, suspecting it is a filter problem Water leakage, moisture, mold, chemical contamination After a long shutdown, reactivation 4. Industry’s lowest mandatory requirement New installation acceptance: 100% leak testing must be conducted After normal use: At least once a year for integrity testing

Here is a set of standard operating procedures for the **High Efficiency Filter Integrity Testing (PAO Leak Detection Method)** commonly used in cleanrooms, specifically for automatic double-door and shower rooms. It is simple, practical, and concise. High Efficiency Filter Integrity Testing (PAO Aerosol Leak Detection) Procedure I. Preparation Tools Aerosol Generator (PAO/DOP) Aerosol Photometer (particle counter can also be used as a substitute) Clean cloth, alcohol, marker pen, record sheet Personnel Wear clean suits, gloves, and masks Equipment Status The door of the shower room is closed, and the room is kept sealed. Clean the outlet surface and nozzles of the high-efficiency filter in advance. II. Dust Generation (Establishing Upstream Concentration) Place the PAO aerosol generator at the inlet end of the shower room (outside the primary filter or in the return air box). Turn on the generator and let the PAO oil mist enter the duct along the airflow and pass through the high-efficiency filter evenly. Take samples in the upstream duct of the high-efficiency filter using the photometer, Adjust the dust generation rate to make the upstream concentration reach 10% to 20% of the photometer’s measurement range and stabilize. Purpose: To ensure that the downstream can accurately detect

Below is a list of the most commonly used and essential tools and materials for installing the main structure of the clean room (generally made of aluminum profiles / square steel / corrugated sheet), which can be directly used for construction, procurement, or scheme writing. I. Common Materials for the Main Structure The main structures of the clean room are usually three types: Industrial aluminum profiles (most commonly used, easy to disassemble, high cleanliness) Galvanized square tubes / square steel (strong load-bearing, low cost) Stainless steel frame (high cleanliness, corrosion-resistant) The following are common tools and materials. II. Essential Installation Tools 1. Measuring and Laying Tools Laser level / level Steel tape measure, right-angle ruler, ink roller Marker pen, chalk 2. Cutting and Processing Tools Profile cutting machine (for aluminum profiles only) Hand drill, impact drill Angle grinder (for grinding, deburring) Drilling tool, drill bit set 3. Fastening Installation Tools Hex key wrench set (for aluminum profiles only) Adjustable wrench, socket wrench Rubber hammer, rubber mallet Screwdriver (cross / flat head) Level, straightedge 4. Auxiliary Tools Ladder, scaffolding Gloves, safety goggles, mask Cables, wiring board III. Installation Materials for the Main Structure 1. Main Frame Materials Industrial aluminum profiles (4040/4080/5050

The selection of the main structure material for the clean room is centered around achieving a balance among cleanliness, load-bearing capacity, corrosion resistance, cost, and ease of installation. The mainstream frameworks include aluminum profiles, stainless steel square tubes, and powder-coated iron square tubes. The enclosures commonly use anti-static PVC curtains, acrylic/PC panels, tempered glass, and color steel plates. 1. Frame Material (Core Load-bearing Structure) 1. Aluminum Profiles (Most Commonly Used) Applicable scenarios: Medium-low cleanliness (ISO 7–8 levels), small and medium-sized, temporary / mobile clean rooms, general areas of electronics / semiconductors. Advantages: Lightweight, quick installation, can be assembled by one person, no heavy equipment required. Surface is anodized, smooth, dust-free, easy to clean, and not prone to dust accumulation. Modular, reusable for disassembly, highly expandable. Disadvantages: Limited load-bearing capacity, not suitable for hanging heavy FFU / equipment. Weak impact resistance, prone to oxidation and discoloration in humid / acid-base environments over long-term use. Selection tips: Prefer 40×40/40×80 industrial purification aluminum profiles, with anodized surface and anti-static treatment. 2. Stainless steel square tubes (304/316, preferred for high-end applications) Application scenarios: High cleanliness (ISO 5–6 levels), pharmaceutical / biopharmaceutical / GMP, food, humid / acid-base corrosive environments. Advantages: 304 Resistant to daily

Wind shower transfer window high-efficiency filter – Standard installation steps I. Pre-installation preparations Stop the machine, disconnect the power supply, and hang the “Equipment maintenance, do not close the switch” sign. Tools needed: Cross-head screwdriver, clean cloth, gloves. Clean the top/back of the transfer window’s fan compartment, wipe off dust. Check the new high-efficiency filter: No damage, no deformation, no moisture or mold Frame is intact, sealant strips are complete The shell has an air flow direction arrow II. Disassembly of the old high-efficiency filter Open the filter maintenance cover (usually on the top or back of the transfer window). Loosen the tightening bolts / clasps, slowly remove the old filter. Clean the installation slot and the interior of the air duct again, without dust or debris. III. Installation of the new high-efficiency filter (key steps) Confirm the direction The air flow arrow on the filter → towards the wind shower chamber and nozzle direction. Place the filter smoothly in the installation slot Hold the frame with both hands, do not touch the filter paper Place it gently in position, without twisting or squeezing Complete the sealing around it Ensure that the sealant strips are fully adhered, without warping or

I. Most Accurate: Check the differential pressure gauge (recommended) Primary filter Normal differential pressure: < 50 Pa Replacement required: ≥ 100 Pa or double the initial value Intermediate filter Normal differential pressure: < 100 Pa Replacement required: ≥ 200 Pa High-efficiency filter (HEPA) Normal differential pressure: < 150 Pa Replacement required: ≥ 300 Pa or significant decrease in air volume II. Most Intuitive: Check the appearance If any of the following conditions are met, it is time to replace the filter: The filter is blackened, yellowed, or heavily clogged with dust The filter paper is damaged, leaking, or deformed The frame seal is detached or cracked The surface has mold spots, is damp, or has water stains III. Most Practical: Check the operating effect When these situations occur, it is basically a clogged filter: The air supply volume of the equipment decreases, and the blowing sensation weakens The air outlet is not uniform or even blocked The door body or box leaks air, makes a whistling sound The pressure difference in the clean area cannot be maintained IV. Mandatory Replacement by Time (Backup Plan) Primary filter: 3 to 6 months Intermediate filter: 6 to 12 months High-efficiency filter: 1 to

Constant-flow air supply ceiling – Core component replacement cycle 1. High-efficiency filters HEPA/ULPA (the most critical consumable) Classical cleanroom / operating room: 1-2 years High usage frequency, large amount of dust: 6-12 months Judgment criteria: Resistance reaches twice the initial resistance or cleanliness does not meet standards → must be replaced 2. Diffusing membranes / diffusers / damping nets PTFE diffusing membranes: 2-3 years Aluminum alloy diffusers: 3-5 years If deformed, clogged, or the effect significantly decreases after cleaning, replace 3. Fans, motors Ordinary centrifugal fans: 5-8 years DC brushless fans: 8-10 years If noise increases, air volume significantly decreases, or abnormal heating → replacement 4. Sealing parts, liquid tank sealant Sealing strips: 1-2 years Liquid tank sealant: 3-5 years If aging, cracking, or air leakage occurs → replace immediately 5. Pressure boxes, frames, shells These belong to structural components and do not need to be replaced regularly Normal use can last 10-15 years with the ceiling One-sentence summary (for your convenience) Filters: must be replaced within 1 year Diffusing membranes: 2-3 years Fans: 5-8 years Sealing parts: 1-2 years

The main structure of the air supply ceiling ( laminar flow air supply ceiling ) typically has a lifespan of 15–20 years, and the core filter components need to be replaced every 1–2 years; daily maintenance mainly involves pressure difference monitoring, filter management, and inspection of seals and structure, ensuring cleanliness and stable airflow. I. Service Life (Standard Operating Conditions) 1. Main Structure (static pressure box, frame, equalizing plate) Design life: 15–20 years (high-quality hot-dip galvanized / stainless steel material) Influencing factors: Material: 304/316 stainless steel > hot-dip galvanized steel > ordinary steel Environment: Humidity, corrosive gases, high dust can shorten the lifespan Maintenance: Regular cleaning, anti-corrosion, and sealing maintenance can extend the lifespan 2. Core Filter Components (filters) Primary efficiency (G4): 3–6 months replacement / cleaning Intermediate efficiency (F8): 6–12 months replacement High efficiency / ultra-high efficiency (H13–U15): 1–2 years replacement (or when the final resistance reaches twice the initial resistance) 3. Seals and Wearable Parts Sealant strips / silicone: 2–3 years replacement Equalizing membrane (PTFE): 5–8 years (with a temperature resistance of 121°C, sterilizable) II. Daily Maintenance (Hierarchical Execution) 1. Daily / Shift (Basic Inspection) Visual inspection: No abnormal noise, vibration, uneven air supply, dust accumulation on the

Conclusion: You can replace it yourself, but there are certain conditions – it’s not just a simple replacement. It must meet the requirements of compliance, sealing, leak detection, and verification. Otherwise, the replacement would be in vain and could even affect the cleanliness level. 1. When can you replace it yourself? If the following conditions are met, you can replace it yourself: You have personnel who understand equipment maintenance (electricians / equipment technicians are sufficient) You have filters of the same specification, size, and qualified (with certificates and test reports) After replacement, simple verification of air velocity, leak detection, and cleanliness can be done The workshop / laboratory does not involve GMP, pharmaceutical, etc. high-level certification (or it is internally allowed to replace by yourself) 2. Key steps for self-replacement (simplified version) Turn off the power, unplug the power supply Remove the decorative cover, trim, and old high-efficiency filter Clean the box, sealing groove, and replace the sealing rubber strip (aging requires replacement) The new high-efficiency filter should have the arrow pointing towards the outlet direction and be evenly pressed Loosen the screws diagonally and tighten them to ensure no air leakage Turn on the machine to measure air velocity,