One Minute To Understand The Usage Specifications And Maintenance of Laminar Flow Pass Box

The laminar flow pass box is an auxiliary equipment for cleanrooms. It is mainly used for transferring small items between a cleanroom and a non-clean area, or between cleanrooms of different grades and pressures. On one hand, it acts as an airlock to prevent pressure loss in the higher-grade cleanroom; on the other hand, it achieves a self-cleaning effect during the transfer process to ensure that items entering the cleanroom are clean themselves, reducing cross-contamination caused by objects. The blow-off time can be adjusted arbitrarily via a manual switch, maximizing both self-cleaning efficiency and energy savings.

I. Laminar Flow Pass Box Installation

Strictly follow the specifications for installation and operation.

Input power: 220V/50Hz. Installation environment temperature: 15°C to 35°C; humidity: 40% RH to 70% RH. 

·When installing the equipment, disconnect the power supply to prevent electric shock. 

·Pay attention to safety when wiring; the enclosure must be grounded. 

·During installation, avoid bumping the equipment casing against other objects to prevent scratching. 

·Strictly follow the installation environment requirements. Failure to comply may affect the performance of the laminar flow pass box and may cause short circuits, resulting in damage to electrical components and shortening the service life of the unit. 

·Install away from heaters, furnaces, or other heat sources. 

·Do not place flammable materials in the installation area to avoid fire hazards. 

·Do not use explosive or volatile chemicals, as inhaling such chemicals may cause fire or explosion. 

·Do not install in environments containing sulfuric acid, hydrochloric acid, or other corrosive chemicals to avoid corrosion and damage to the unit. 

·After installation, wipe the inside and outside of the enclosure clean. 

·The recommended filter replacement cycle is: initial resistance × 2 = final resistance at replacement.

II. Pre-Operation Checks

Filter efficiency and airflow velocity testing

·Confirm that the external power supply is properly connected and the power supply is adequate. 

·Check whether the return air screen is blocked, as blockage may prevent normal operation and cause functional abnormalities or damage to electrical components. 

·Start the pass box according to the operating instructions. The fan should operate normally for the set time without significant noise or abnormal vibration. 

·The door interlock should function properly (when one door is opened, the other door cannot be opened). The UV germicidal lamp should turn on and off according to the set time.

·Filter efficiency test for laminar flow pass box: Use a PAO aerosol photometer and an aerosol generator to perform integrity testing on the gel-seal HEPA filter at a distance of 25.4 mm from the air outlet surface, with a scanning speed not exceeding 5 mm/s. The leak rate should be less than 0.01% (start the unit and allow it to self-clean for at least 10 minutes before testing).

·Airflow velocity test for laminar flow pass box: Use an anemometer to measure the airflow velocity 100-150 mm below the air outlet surface. The average velocity should be between 0.35 and 0.65 m/s.

III. Precautions for Use

Strictly follow the specifications for use and operation.

·Wiring must be done according to the wiring instructions to avoid incorrect port connections. Power must be disconnected during wiring or maintenance.

·Do not use chemical solvents such as thinner to clean the stainless steel body.

·The power board uses digital circuits; keep it as far away as possible from high-frequency or high-current devices to avoid system freezes.

·Do not allow foreign objects to enter the ports to prevent short circuits.

·Do not operate the buttons on both sides simultaneously, as this may cause the system to freeze. If a freeze occurs, simply turn off the power.

·Do not blow compressed air directly at the HEPA filter from a close distance.

·The ultraviolet (UV) germicidal lamp can penetrate cells and cause cell death. Therefore, when using the UV lamp for disinfection, avoid direct exposure to human skin, especially the eyes. Do not look directly at the lamp when it is on. Since short-wave UV light does not penetrate ordinary glass, wearing glasses can protect your eyes from injury. If eye injury occurs accidentally, it is generally not serious—similar to sunburn on the eyes. In severe cases, eye drops or breast milk can be used to aid recovery.

·When replacing the germicidal lamp, disconnect the power supply and allow the lamp to cool down before replacement to prevent burns from the high-temperature lamp.

IV. Maintenance

Maintenance must be performed by professionally trained personnel.

The laminar flow pass box equipment must be maintained and serviced by professionally trained personnel. If any abnormal condition is found, immediately disconnect the power supply and take corrective action.

01 Fan and Motor

The centrifugal fan must rotate smoothly without abnormal noise or vibration. If abnormal noise is heard, check whether there are foreign objects inside the blower and whether the motor bearing sound is abnormal. If the motor is faulty, replace the motor.

02 Germicidal Lamp

The germicidal lamp should operate normally without flickering or extinguishing.

03 Control Panel

The control panel buttons should function normally, and adjustments should operate properly.

04 Differential Pressure Gauge

The control panel buttons should function normally, and adjustments should operate properly.

05 Unit Exterior

Check the unit exterior for scratches or corrosion.

Q:Periodic inspection of the motor

A: Acceptance criteria: 

Check whether the motor has abnormal noise, vibration, or odor. 

Check for abnormal bearing noise. Inspect cables and terminals for damage or corrosion.

Signs and possible causes: 

Bearing damage causing rough motor operation or locking.

Poor insulation at power connections or terminals causing abnormal heating; incorrect grounding; short circuit, etc.

Q:Periodic inspection of the fan

A:Acceptance criteria: Check the centrifugal fan for abnormal noise, vibration, or damage. Replace defective parts.

Signs and possible causes: 

Dust accumulation or damage causing unbalanced operation and subsequent damage.

Q:Periodic inspection of the outer casing and other components

A:Acceptance criteria: Visually inspect components for defects, discoloration, scratches, etc.

Signs and possible causes: Corrosion or rusting of components caused by chemical agents, generating dust.

Q:Periodic inspection of other electrical components and wiring materials

A:Acceptance criteria: Check for rust, exposed conductors, damaged wire insulation, etc.Signs and possible causes: Poor insulation due to dust; overheating, short circuit, or burnout caused by loose terminal screws.

Q:Periodic PAO test

A:Acceptance criteria:

1. Before testing, the laminar flow pass box must be fully functional and operational in all aspects, meeting its technical performance requirements.

2. Before testing, ensure there is no smoke leakage from the test instrument or its connection to the equipment, preventing smoke from entering the working area of the pass box and affecting the test results. (If smoke leakage is unavoidable, take protective measures.)

3. After the pass box operation stabilizes (approximately 3 minutes), start the PAO aerosol generator. Use a calibrated photometer to measure the PAO concentration inside the pass box. When the concentration reaches ≥10 μg/L, begin testing according to the instrument operating procedure.

4. During the test, scan the HEPA filter and its mounting frame for leaks using a sampling probe at a distance of approximately 25 mm from the outlet surface, at a speed not exceeding 5 cm/s.

5. The leak rate should be less than 0.01%.

Q:Static airborne particle count test

A:Acceptance criteria:

1. Under static conditions, use calibrated instruments to measure airborne particles ≥0.5 µm and ≥5.0 µm inside the laminar flow pass box.

2. Before testing, the pass box must be fully functional and operational, meeting its technical performance requirements.

3. Turn on the pass box, press "Fan" and let the fan run for approximately 3 minutes, then place the test instrument at the sampling points.

4. Sampling points are arranged within the area under the filter. Number of sampling points: 2. Sampling frequency: one sample per point. Sampling volume: minimum 1 m³ per sampling point. Record the actual sampling volume and actual reading.

Signs and possible causes: Leakage due to filter damage.

Q:UV lamp irradiance test

A:Acceptance criteria:

1. After the UV lamp has been on for 5 minutes, place the probe of a UV irradiance meter (wavelength 254 nm) at the center, 1 meter vertically below the UV lamp being tested. After the meter stabilizes, the reading is the irradiance value of the UV lamp.

2. Precautions during measurement: Test voltage 220V, temperature 20°C-25°C, relative humidity <60%. The UV irradiance meter must be used within its calibration validity period.

Acceptable value: ≥70 μW/cm².Signs and possible causes: UV lamp has exceeded its service life; insufficient irradiance affects sterilization effectiveness.

Q:Noise test

A:Acceptance criteria: Use a calibrated sound level meter to measure the equipment noise at a distance of 1.2 meters from the equipment. Turn off the equipment; measure the ambient noise as background noise. When the difference between the measured value and the background noise is below 9 dB(A), apply a correction factor. The corrected value is the measurement result. Apply correction as follows:

A) Difference <3 dB(A): Test invalid.

B) Difference = 3 dB(A): Correction factor = -3.

C) Difference = 4–6 dB(A): Correction factor = -2.

D) Difference = 7–9 dB(A): Correction factor = -1.

E) Difference ≥10 dB(A): No correction.

Standard: Noise should be ≤65 dB.Signs and possible causes: Abnormal fan operation causing excessive noise.

V. Troubleshooting

Electrical function, cleanliness, and airflow velocity testing

01 Electrical Function Abnormalities

When the equipment malfunctions, perform repairs according to the instruction manual or contact our customer service hotline for on-site repair. For products within the warranty period, our company will not charge any repair fees (excluding damage caused by human factors). For products beyond the warranty period, our company will charge corresponding fees based on the replacement parts used.

Note: Self-modification of the electrical circuit is not covered under warranty. Filters and lamps are consumables and are not covered under warranty.

02 Cleanliness Test Abnormalities

When the cleanliness test does not meet the technical specifications, check whether the filter paper of the HEPA filter is damaged and whether the filter clamping blocks are properly tightened. If both of the above are satisfactory and leakage still exists, wipe the filter frame with alcohol and re-test. If the filtration efficiency still does not meet the requirements, replace the HEPA filter.

03 Airflow Velocity Test Abnormalities

When the measured average airflow velocity of the fan filter unit falls below 0.36 m/s, verify whether the fan is operating normally. If the fan is not operating normally, perform repairs according to the instruction manual or contact our customer service hotline for on-site repair. If the fan is operating normally, replace the pre-filter or HEPA filter.

HEPA Filter Replacement Procedure:

a. Disconnect the power supply and prepare the new HEPA filter for replacement.

b. Use a wrench to remove the screws (counterclockwise) securing the diffuser plate on the air outlet side of the laminar flow pass box, then remove the diffuser plate.

c. Use a wrench to remove the screws of the filter clamping blocks inside the pass box, then take out the old filter.

d. When installing the new filter, unpack it and inspect its appearance, including checking for any damage to the filter paper, deformation of the frame, or joint gaps. Secure the filter using the clamping blocks and nuts, without applying excessive force.

e. After replacing the HEPA filter, confirm that there is no leakage around the frame and perform a PAO test to ensure it meets the technical specifications. Normal operation can only resume when the average airflow velocity is maintained within 0.45 m/s ±20%.