Technical Guidelines For Replacement And Installation Of High Efficiency Air Filters in Biosafety Cabinets

The replacement of HEPA/ULPA filters in biosafety cabinets is a high-risk, high-tech operation that must be carried out by personnel who have received professional training and are equipped with appropriate tools. Incorrect installation will directly lead to the failure of the protective function of the safety cabinet. The following are detailed technical guidelines and standardized processes.
Core principle: Safety first, zero leakage installation. The replacement process itself is a potential biological hazard to the operator and environment, and must strictly comply with biosafety regulations.

1. Safety and risk assessment
Identify risk: The old filter may have been contaminated with pathogens. The entire operation must be carried out under appropriate biosafety level protection (at least equivalent to the highest risk level handled by the safety cabinet).
Personnel requirements: At least two personnel must work together and wear appropriate personal protective equipment, including protective clothing, gloves, goggles, and respiratory protection (such as N95 masks or powered air respirators, depending on the risk).
Environmental preparation: Conducted during non peak hours in the laboratory, designated work areas, and posted warning signs.
2. Preparation of tools and materials
New filter: Confirm that the model, size, and efficiency are completely matched, and its' Factory Leak Detection Qualification Report 'has been verified.
Professional tools:
Aerosol generators (such as PAO, DOP) and aerosol photometers (used for leak detection after installation).
Efficient sealant (polyurethane or silicone type, usually pre coated or equipped with sealing gasket for new filter frames).
Non fluffy cloth, plastic bag (used to wrap old filters), label.
Suitable wrenches, screwdrivers, hex keys, etc. (for disassembling panels).
Torque wrench (as required by installation instructions).
Disinfectants (such as 70% isopropanol, diluted bleach), biohazard waste bags.
Personal protective equipment: as mentioned earlier.
3. Biosafety cabinet handling
Purification: Before closing, let the safety cabinet run in a non interfering state for at least 10 minutes to purify the work area.
Surface disinfection: After shutting down, thoroughly wipe all surfaces inside the cabinet with disinfectant, especially the area around the filter.
Power outage and identification: completely disconnect the power supply, lock and tag to prevent accidental startup.

4. Disassembly operation
Remove internal components: Carefully remove all removable inner lining panels, diffuser plates (flow screens), etc., and place them in a disinfectant bag or soak them in disinfectant solution.
Contact filter: Wear PPE properly.
Disassemble the fixing device: According to the manufacturer's manual, disassemble the pressure strip, fixture, or bolt that fixes the filter in sequence. Pay attention to recording the disassembly sequence and position.
Remove filter:
Key step: Two operators collaborate, one holding onto the filter while the other completely loosens the fastener.
Put the old filter directly into a pre prepared thick plastic bag labeled with a biohazard label. The movement should be smooth, with minimal shaking to prevent residual aerosols from escaping.
Immediately seal the plastic bag.
5. Handling and Cleaning
Packaging: Place the sealed old filter into the second layer of biohazard waste bag and perform high-pressure sterilization or treat it as infectious waste according to laboratory regulations.
Deep cleaning of the cavity: Thoroughly wipe and clean all exposed areas such as the filter installation groove, cavity walls, and fan static pressure box with disinfectant. Ensure no dust or residual colloids. Wait for complete drying.

6. Pre installation inspection
Check again: Verify the model and airflow direction arrow of the new filter.
Inspection: Visually inspect the frame and filter material of the new filter for any physical damage caused during transportation.
Prepare for sealing: If using independent sealant, prepare according to the instructions. If the filter is equipped with a self sealing gasket, check if it is intact and flat.
7. Installation operation
Positioning: Two people collaborate to smoothly and accurately place the new filter into the installation slot. Be sure to ensure that the airflow direction arrow points correctly (for supply air filters, the arrow usually points to the working area; for exhaust air filters, the arrow points to the exhaust direction).
Initial positioning: Press the filter frame evenly with your hand to make it preliminarily positioned.
Installation of fixed devices:
Install inner liner or diffuser plate (if applicable).
Reinstall the pressure strip, fixture, or bolt according to the manufacturer's specified sequence and torque.
Key: The fasteners must be tightened diagonally, step by step, and evenly to ensure even force distribution on the filter and prevent leakage caused by frame deformation. Use a torque wrench to tighten to the specified value.
After installation inspection: Confirm that all components have been reset and there are no tools or debris left in the cavity.

This is the only criterion for determining whether the installation is successful or not.
8. Integrity scanning leak detection test
Test preparation: Reconnect the power supply, but do not start the safety cabinet fan. Set up aerosol generators and photometers by professionals.
Upstream dust generation: Inject aerosols upstream of the filter (the supply air filter is usually located in the fan compartment, and the exhaust air filter is located in the working area).
Downstream scanning:
Start the photometer and use the probe to perform a slow, overlapping scan at a speed of no more than 3cm/s on the entire cross-section downstream of the filter, at all seams, and at the sealing points between the frame and the box.
The scanning path should cover all areas.
Qualification assessment:
Maximum allowable leakage rate: The reading at any point shall not exceed 0.01%.
If the scan passes, record the test report.
If a leak is detected: the cause must be immediately investigated. It may be due to uneven installation, sealing gasket issues, defects in the filter itself, or damage to the casing. After troubleshooting, it is necessary to rescan until it is fully qualified.
9. Performance running test
After passing the airtightness leak detection, open the safety cabinet and run it for at least 30 minutes.
Measure and record: face wind speed, descending wind speed, airflow smoke mode (optional, but recommended). Ensure that all parameters comply with the standard (such as YY 0569).
Alarm test: Test whether all sound and light alarm functions are normal.

This is key evidence of quality system and compliance.
Update log: Record the replacement date, filter serial number, and replacement personnel in the maintenance log of the biosafety cabinet.
File archiving: Permanently archive the following files:
The 'Factory Leak Detection Qualification Report' for the new filter.
After this replacement, the on-site integrity scanning leak detection test report must be signed and dated by the operator.
Performance run test data.
Disposal records of old filters.
Absolutely prohibited items
Single person operation is prohibited.
It is prohibited to put it into use without conducting integrity leak testing.
Do not use damaged or questionable filters.
Do not operate without wearing appropriate PPE.
Do not skip disinfection and cleaning steps.
summary
Replacing the high-efficiency filter of the biosafety cabinet is essentially a reconstruction of the core protective barrier. The core technology can be summarized as follows:
Rigorous preparation, safe disassembly, precise installation, and rigorous verification.
Any negligence in any link may lead to barrier failure. For most institutions, entrusting this work to qualified professional service engineers authorized by equipment manufacturers is the most reliable and compliant choice. They have specialized tools, standard procedures, and extensive experience, and can provide legally binding verification reports to ensure that your biosafety cabinet remains in a safe and reliable protective state after replacement.