Laminar Flow Hood or Cabinet Definition

Utilizing screens to trap all particles approaching the cabinet, a Laminar flow hood or cabinet may be utilised to produce a clean working environment.

• These cabinets are designed to conceal the operation from the atmosphere and are ideal for plate pouring and the aseptic delivery of certain media.
• The only difference between laminar flow and biosafety cabinets is that laminar flow cabinets provide effluent air directly to the consumer’s face.
• In a biosafety cabinet, both the user and the sample are protected, but in a laminar flow cabinet, just the sample is protected.

Laminar Flow Hood or Cabinet

Components/ Parts of Laminar flow hood

The components of a laminar flow cabinet are as follows:

1. Cabinet

• Since the cabinet is composed of stainless steel, there are few to no holes or cracks that may harbour spores.
• The cabinet insulates the internal environment produced by it and protects the laminar flow from the external atmosphere.
• A glass shield is attached to the front of the cabinet, and depending on the laminar cabinet, it may open completely or have two apertures for the user’s hands.

2. Working station

• Inside the cabinet is a flat work surface where all activities will be carried out.
• At the workstation where the procedure is performed, culture plates, a burner, and loops are all put in place.
• To avoid corrosion, the worktop is likewise composed of stainless steel.

3. Filter pad/Pre-filter

• The top of the cabinet has a filter pad, via which air enters the cabinet.
• The filter mat prevents dirt particles and certain germs from invading the workspace of the cabinet.

4. Fan/Blower

• Under the filter pad, there is a fan that draws in air and circulates it within the cabinet.
• The fan also enables air to travel in the direction of the HEPA filter, trapping any leftover microorganisms as they go through the filter.

5. UV light

• The inside of the cabinet and its contents may be sterilised before the procedure using a UV germicidal light used in certain laminar flow hoods.
• To avoid UV exposure to the user’s body surface, 15 minutes prior to the operation, the UV light must be activated.

6. Fluorescent light

• To provide enough lighting throughout the procedure, fluorescent lighting is installed within the cabinet.

7. HEPA filter

• Within the cabinet, there is a High-efficiency Particulate Air Filter, which improves the sterility of the atmosphere for the operation.
• The air is sent through the filter, which collects germs, fungi, and various dusty bits.
• The filter keeps the cabinet’s inside sterile, minimising the possibility of infection.

Laminar Flow Hood or Cabinet

Principle/ Working of Laminar flow hood

• The operational idea of a laminar flow cabinet is predicated on the laminar flow of air via the cabinet.
• To generate a dust-free atmosphere, the device uses an inward flow of air that passes through a minimum of one HEPA filter.
• The air is sucked in, processed via a filtering system, and then discharged over the operating area as part of the laminar air flow.
• The filter pad, or pre-filter, provides for smooth airflow entering the cabinet by first passing the air through it.
• The air is then directed toward the HEPA filters by the blower or fan.
• The HEPA filters subsequently collect bacteria, fungi, and other particulate contaminants, so that the air exiting the system is free of particles.
• The majority of the effluent air exits the cabinet towards the operator’s face while passing over the workbench, which is where the majority of the cabinet’s perforations are located.
• To stop polluted outside air from entering the cabinet, all angles of the laminar flow hood are sealed, and continuous positive air pressure is maintained.

Laminar Flow Hood or Cabinet

Procedure for running the laminar flow cabinet

The following are the actions to take while utilising a laminar flow cabinet:

1. Before running the laminar flow cabinet, the cabinet should be inspected to ensure that no UV-sensitive items are present.
2. The UV light is then activated and the hood’s glass cover is closed.To ensure that the surface of the operating table is sterile, the UV light should be on for about 15 minutes.
3. The UV light is then switched off, and the airflow is not activated for about 10 minutes.
4. The airflow is activated about five minutes before the commencement of the treatment.
5. The glass barrier is then opened, and the fluorescent light is switched on simultaneously.
6. The working surface of the cabinet may be sterilised with additional disinfectants, such as 70% alcohol, to offer more protection.
7. The airflow, fluorescent bulb, and glass shield are all closed when the task is over.

Different types of laminar flow cabinets

There are two types of laminar flow cabinets dependent on the airflow direction:

1. Vertical laminar flow cabinet

• In vertical flow cabinets, air flows vertically from the top to the bottom of the cabinet.
• Because a horizontal airflow hood requires greater depth and floor space, a vertical airflow working bench is more controllable and less likely to cause airflow obstructions or the transfer of polluted air downstream.
• It is believed that the vertical laminar flow cabinet is safer since it does not direct air directly towards the experimenter.

2. Horizontal laminar flow cabinet

• The ambient air enters the horizontal laminar flow cabinets from behind the workbench and is directed by the blower towards the HEPA filters.
• The filtered air is then horizontally discharged into the office setting.
• This cabinet has the benefit of cleaning the environment with constant velocity airflow parallel to the workspace.
• The operator is immediately struck by the elluent air, which might lower the security level of these laminar flow cabinets.

Uses of Laminar flow hood

A laminar flow cabinet is often used in the laboratory for the reasons listed below:

1. In labs, contamination-sensitive procedures like plant tissue culture employ laminar flow cabinets.
2. Inside the cabinet, further laboratory procedures such as media plate preparation and organism culture may be carried out.
3. Electronic equipment that is sensitive to particles is operated within the cabinet.
4. To maintain a particle-free atmosphere for the activities, medication preparation processes are also carried out within the cabinet in the pharmaceutical industry.
5. Laminar flow cabinets may be custom-made for certain specialty tasks and utilised for standard lab procedures in both the microbiological and industrial sectors.

Precautions

The following considerations should be kept in mind while using the laminar airflow:

• UV light sterilisation of the laminar flow cabinet is required both before and after the procedure.
• Airflow and UV light shouldn’t be used together.
• When the UV light is turned on, no operations should be done.
• The operator should wear long gloves and a lab coat.
• Before and after work is finished, the workbench, glass shield, and other items within the cabinet should be sterilised.

References and Sources

• Collins CH, Patricia M, and Lyne JM (1995). Collins and Lynes Microbiological Methods 7th edition. Grange, Butter Worth, Oxford.
• 5% – https://www.lamsys.com/products/vertical_laminar_flow/
• 2% – https://www.laminarflows.co.uk/
• 1% – https://magnaflux.eu/en/Resources/FAQs/FAQs-UV-Lamps
• 1% – https://en.wikipedia.org/wiki/Laminar_flow_cabinet
• <1% – https://www.trane.com/residential/en/products/indoor-air-quality/cleaneffects/
• <1% – https://www.sciencedirect.com/topics/immunology-and-microbiology/laminar-flow-cabinet
• <1% – https://www.safety.rochester.edu/ih/uvlight.html
• <1% – https://www.light-sources.com/solutions/germicidal-uvc-lamps/uv-germicidal-lamps/uv-germicidal-bulb/
• <1% – https://www.labogene.com/Biological-Safety-Cabinets
• <1% – https://www.filtermakers.com.au/hepa-filter/
• <1% – https://www.diamed.bg/upl_doc/Aquaria%20product%20catalog_Laminarni_boksove.pdf
• <1% – https://www.chegg.com/homework-help/definitions/the-path-of-airflow-in-humans-14