What issues should be noted during the installation and maintenance of high-efficiency exhaust units?

The installation and maintenance of the high-efficiency Exhaust Unit (HEPA Exhaust Unit) directly affect its filtration efficiency, system stability, and safety. Especially in scenarios such as biosafety laboratories and clean workshops, the norms must be strictly followed. The following are the key precautions and operational points:
I. Installation stage: Ensure that the airflow is compliant and the equipment is stable
1. Installation environment and layout requirements
Space reservation
At least 50cm of maintenance space should be reserved around the equipment, and at least 1 meter of height should be reserved at the top for filter replacement (which needs to be combined with hoisting equipment or lifting platforms).
Example: In the BSL-3 laboratory, the exhaust unit should be installed above the ceiling of the contaminated area and connected to the indoor exhaust outlet through sealed pipes.
Airflow direction control
It is essential to ensure the "unidirectional flow" principle: indoor air → exhaust duct → high-efficiency exhaust unit → outdoor safe area (away from fresh air intakes and areas where people are active).
The horizontal distance between the exhaust outlet and the fresh air inlet should be no less than 10 meters, and the vertical distance (with exhaust at the top) should be no less than 3 meters to prevent an airflow short circuit.
2. Pipe connection and sealing
Pipe material:
In biosafety scenarios, stainless steel or galvanized steel plate air ducts should be used, with smooth inner walls and no dead corners. For welded or flange connections, air tightness tests should be conducted (leakage rate ≤0.01%).
In environments with hazardous chemicals, corrosion-resistant materials (such as PP air ducts) should be selected and grounded to prevent static electricity accumulation.
Soft connection requirements:
Silicone or fluoro rubber expansion joints (15-20cm in length) should be installed at the inlet and outlet of the equipment to reduce the transmission of vibration and avoid sparks caused by metal friction.
3. Equipment fixation and vibration reduction
Hoisting method:
It is fixed to the main structure of the building with expansion bolts and spring vibration-damping hangers. It is strictly prohibited to install it directly on the ceiling keel.
The spacing of the vibration-damping hangers should be no more than 2m to ensure that the levelness deviation of the equipment is no more than 2mm/m, preventing the deformation of the filter frame and air leakage due to vibration.
4. Electrical and Automatic Control Systems
Explosion-proof design
Inflammable and explosive scenarios (such as hazardous chemical warehouses), explosion-proof motors, switches, and circuits should be used, in compliance with GB 50058 "Code for Design of Electrical Installations in Explosive Hazardous Areas".
Interlocking control
Linked with the supply fan, differential pressure sensor, and fire alarm system:
When the supply fan malfunctions, the exhaust unit needs to be shut down with a delay of 5 to 10 minutes to maintain negative pressure in the room and prevent the spread of pollution.
When a fire alarm is triggered, the power supply to the fan will be automatically cut off and the fire damper will be closed.
Ii. Maintenance Phase: Ensure filtration efficiency and operational safety
1. Daily inspection of contents
Check the abnormal handling measures for the qualified standards of the inspection items
When the operating noise is ≤65dB (1 meter away from the equipment), check for loose vibration-damping hangers or dust accumulation on the impeller, and clean or tighten them
There should be no condensation, deformation, or air leakage marks on the appearance of the pipeline. Use sealant to repair the leakage or replace the damaged parts
The real-time resistance reading of the differential pressure gauge should be ≤ 80% of the final resistance (for example, the initial resistance is 250Pa and the final resistance is 500Pa). When approaching the final resistance, the filter needs to be planned for replacement
If the current within ±10% of the rated current of the fan is too large, it may be due to excessive load. Check whether the filter is clogged
2. Key points for filter replacement
Replacement cycle:
Conventional scenarios: Every 1-2 years (replace when the differential pressure gauge shows approaching the final resistance).
High-risk scenarios (such as handling pathogens and radioactive aerosols): Mandatory replacement is required every 6 to 12 months, or the cycle can be shortened based on the frequency of use.
Safety operation procedures (taking a biosafety laboratory as an example) :
Pre-disinfection: Before replacement, turn on the in-situ disinfection module in the unit (such as ultraviolet lamp irradiation for 30 minutes, or vaporized hydrogen peroxide (VHP) circulation for 1 hour).
Protective equipment: Operators should wear Class A protective suits, N95 masks, and chemical protective gloves, and disassemble the old filter in a negative pressure environment.
Sealing treatment: The old filters are placed in leak-proof plastic bags, marked with the "Contamination" label, and disposed of as medical waste or hazardous waste (in compliance with HJ 421 "Standard for Special Packaging Bags, Containers and Warning Signs for Medical Waste").
Leak detection test: After the new filter is installed, a scanning leak detection is conducted using an aerosol photometer. The leakage rate should be less than 0.01% (ISO 14644-3 standard).
3. Maintenance of key components
Fan impeller cleaning
Check the dust accumulation on the impeller every quarter. Wipe it with compressed air (≤0.4MPa) or neutral cleaner. Avoid damaging the impeller surface with steel wool balls.
In corrosive environments, the impeller needs to be coated with anti-corrosion coatings (such as epoxy resin), and the integrity of the coating should be inspected annually.
Sensor calibration
The differential pressure sensor and wind speed sensor should be calibrated once every six months. Use a standard instrument (such as a micro-differential pressure gauge) to compare the measured values. When the error exceeds 5%, adjustment or replacement is required.
Electrical system inspection
Check the lubrication condition of the motor bearings annually and add high-temperature resistant grease (such as lithium-based grease). Check whether the insulation layer of the circuit is aged and tighten the terminal blocks to prevent poor contact.
4. Key points for maintaining special scenarios
Radioactive scene:
Maintenance personnel are required to wear personal dosimeters and keep their operation time within 30 minutes (to reduce radiation exposure).
The surface contamination level of the equipment should be less than 0.4Bq/cm² (alpha rays). When it exceeds the standard, it needs to be cleaned with a special detergent and tested.
High humidity environment
Drain the condensate collection tank every week to prevent the growth of microorganisms. The filter frame should be made of stainless steel to prevent rusting and air leakage.
Iii. Safety and Compliance Requirements
Compliance with regulations and standards
Biosafety: It must comply with GB 19489 "General Requirements for Laboratory Biosafety". When replacing the filter, microbial culture verification is required (for example, if the surface wipe sample of the old filter is inoculated into the culture medium and no colonies grow after 48 hours of culture).
Cleanroom: By ISO 14644-1, the concentration of dust particles needs to be retested after maintenance to ensure that the cleanliness level meets the standards.
Occupational health: During the maintenance process, the concentration of indoor harmful gases (such as VOCs and formaldehyde) should be monitored to ensure compliance with GBZ 2.1 "Occupational Exposure Limits for Hazardous Factors in the Workplace".
2. Recording and Traceability
Establish maintenance files, including:
Filter replacement date, brand, model, and leak detection report.
Sensor calibration records, fault handling situations, and signatures of maintenance personnel.
The retention period of the archives: is at least 5 years (permanent preservation is required in high-risk scenarios).
Iv. Troubleshooting and Handling of Common Faults
Possible causes and solutions for fault phenomena
When the air volume drops, the filter is clogged, or the fan impeller is worn, replace the filter, repair the impeller, or replace the fan.
Insufficient indoor negative pressure, air leakage in pipelines, imbalance of exhaust/supply air balance, air tightness detection, and leak repair, adjustment of supply and exhaust air ratio
The motor overheats and stops. The bearings lack oil. The power supply voltage is unstable. Add grease and check the power supply system.
The alarm system mistakenly triggers sensor faults, and incorrect parameter Settings, calibrates or replaces sensors, and resets thresholds.
Summary: Key points of full-cycle management
Installation: Focus on the airflow direction, sealing performance, vibration reduction, and fixation to ensure system compliance.
Maintenance: With the filter as the core, combined with daily inspection, regular replacement, and sensor calibration, the filtration efficiency is guaranteed.
Safety: For different risk-level scenarios, corresponding protective measures (such as disinfection, explosion prevention, and radiation protection) are taken, and strict records are kept for traceability.
Through systematic installation norms and maintenance procedures, the service life and safety of high-efficiency exhaust units can be maximized, avoiding environmental pollution or personnel exposure risks caused by equipment failures.