What are the precautions for the daily application of laminar flow hoods?

Laminar flow hoods must strictly follow operation norms and maintenance standards in daily applications to ensure their clean effect and equipment safety. The following are the core precautions in daily applications, classified and explained by scenarios and operation dimensions:
I. Preparations and Inspections before Operation
1. Basic inspection before equipment startup
Power supply and circuit: Confirm that the power supply voltage is consistent with the rated voltage of the equipment (such as 220V/380V), and check if the wires are damaged to avoid short circuits causing malfunctions.
Filter status: Check the resistance value of the high-efficiency filter (HEPA/ULPA) through the differential pressure gauge. If it exceeds 1.5 times the initial resistance (for example, the initial resistance is 200Pa and now it has reached 300Pa), it needs to be replaced in time to prevent insufficient air volume from affecting the cleanliness.
Fan and motor: Before starting, manually rotate the fan impeller to ensure there is no jamming or abnormal noise, to prevent motor overload and burnout.
2. Confirmation of environmental adaptability
Installation location: The laminar flow hood should be kept away from sources of airflow disturbance such as doors, Windows, and air conditioning outlets, and maintain a distance of ≥50cm from the wall to ensure smooth air intake. If it is a vertical flow laminar flow hood, the installation height should be 1.2-1.5 meters away from the working surface to avoid an airflow short circuit.
Temperature and humidity control: In medical/pharmaceutical scenarios, it is necessary to cooperate with an air conditioning system to keep the ambient temperature between 18 and 26℃ and the humidity between 45% and 65%, to prevent high temperature/high humidity from causing a decline in filter efficiency or equipment condensation.
Ii. Operating Norms during Operation
1. Airflow management and interference control
Face velocity monitoring: Use an anemometer to regularly measure the working face velocity (vertical flow is recommended to be 0.36-0.54m/s, horizontal flow 0.45±0.2m/s). If the velocity is 20% lower than the standard value, it is necessary to check whether the filter is clogged or the fan speed is normal.
Personnel and item movement: During operation, avoid rapid walking or frequent hand raising in front of the laminar flow hood to prevent interference with the unidirectional flow airflow. Items should be slowly placed in the working area from the side to avoid blocking the air intake from the front.
2. Special operations in different scenarios
Medical/biosafety scenarios:
Before surgery or microbiological experiments, the laminar flow hood should be opened 30 minutes in advance. The operation can be carried out only after the airflow stabilizes. After use, the UV lamp should be turned on for sterilization for more than 30 minutes (note to avoid direct ultraviolet radiation on the human body).
When handling infectious samples (such as COVID-19 sampling), it is necessary to ensure that the exhaust of the laminar flow hood is connected to the high-efficiency filtration system of the biosafety cabinet to prevent aerosol leakage.
Electronic/semiconductor scenarios:
Operators should wear anti-static clothing and shoe covers. Tools should be wiped and disinfected with alcohol to prevent static electricity from attracting fine dust (the anti-static grounding resistance should be ≤10Ω).
The use of volatile solvents (such as acetone) in the laminar flow hood is prohibited to prevent corrosion of the filter or the risk of explosion.
Iii. Key Points for Daily Maintenance and Disinfection
1. Cleaning frequency and methods
Daily cleaning: Wipe the inner walls of the laminar flow hood, the workbench surface, and the lampshade with 75% alcohol to remove dust and stains. In medical Settings, it is necessary to focus on wiping the metal surfaces near the surgical area to prevent bacterial growth.
Weekly deep cleaning: Disassemble detachable parts (such as grilles and air intake screens), soak and clean them in a neutral detergent, dry them, and then reinstall them. The pharmaceutical workshop needs to be sterilized with formaldehyde fumigation or vaporized hydrogen peroxide (VHP). After sterilization, it should be ventilated for 4 to 6 hours to remove the residue.
2. Filter and consumable replacement
High-efficiency filter (HEPA): In normal environments, it should be replaced every 1-2 years. In highly polluted scenarios (such as operating rooms), it needs to be replaced every 6-12 months. When replacing, wear dust-proof clothing, turn off the fan, and disassemble it in the order of "exhaust first, then supply" to prevent contaminants from spilling.
Primary filter: Check it once a month. If there is obvious dust on the surface (such as blackening), it needs to be blown clean with compressed air or replaced directly (it is recommended to replace it every 3 to 6 months).
Iv. Safety and Emergency Response to Faults
1. Safety protection measures
Electrical safety: The laminar flow hood needs to be grounded for protection (grounding resistance ≤4Ω) to avoid the risk of leakage. When conducting maintenance, the power supply must be cut off first. It is strictly forbidden to operate with power on.
Biosafety: After handling pathogen samples, the interior of the laminar flow hood and the filters need to be disinfected in situ (such as high-temperature steam sterilization), and then the filters should be replaced by professionals to prevent microbial leakage.
2. Common Faults and Solutions
Insufficient air volume: It may be due to a clogged filter or aging of the fan capacitor. First, check the resistance of the filter. If it is normal, replace the capacitor or the fan.
Abnormal noise: If the fan makes abnormal noises, it might be due to worn bearings. Lubricating oil should be added or the bearings replaced. If the airflow whistles, it might be that the air intake is blocked and the air intake screen needs to be cleaned.
The cleanliness does not meet the standard: If the number of particles ≥0.5μm exceeds the standard through the detection of a dust particle counter (for example, > 3520 particles /m³ in the 100-level zone), the high-efficiency filter should be replaced immediately and any air leakage points should be checked (the smoke method can be used to detect whether the sealing gasket is aged).
V. Additional Precautions for Special Scenarios
Pharmaceutical GMP compliance requirements
Laminar flow hoods need to be regularly tested for "suspended particles", "settling bacteria" and "surface microorganisms". The data should be recorded and archived to ensure compliance with the A-level clean area standard (settling bacteria ≤1CFU/dish).
The sterilization record should include the disinfection time, the concentration of the disinfectant, and the signature of the operator for audit verification.
2. Usage Specifications for Mobile Laminar Flow Hoods
When used outdoors, avoid rain exposure. For battery-powered types, ensure sufficient battery power (it is recommended that the backup power supply last for at least 4 hours). During the movement, the filter compartment door should be fixed to prevent damage to the filter caused by vibration.
Summary
The daily application of laminar flow hoods needs to take into account both "equipment performance maintenance" and "scene safety adaptation". From parameter calibration before startup to airflow management during operation, and then to periodic disinfection and filter replacement, each link must strictly follow the standard operating procedures (SOP). Especially in scenarios such as medical and pharmaceutical industries where there is zero tolerance for pollution, any negligence may lead to the failure of cleanliness. It is necessary to ensure the long-term stable operation of laminar flow hoods by regularly training operators and establishing maintenance ledgers (recording filter replacement times, disinfection frequencies, etc.).