Laminar Flow Hood/Cabinet: Definition, Parts, Principle, Types, Uses (2023)

A laminar flow hood/cabinet is an enclosed workstation used to create a contamination-free work environment by using filters to capture any particles entering the cabinet.

• These cabinets are designed to protect work from the environment and are very useful for the aseptic distribution of certainmediajpour the plate.
• Laminar flow booths are similar to biosafety booths, with the only difference being that in laminar flow booths, the outflow air is directed towards the user's face.
• In a biosafety cabinet both the sample and the user are protected, while in the laminar flow cabinet only the sample and not the user is protected.

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Components/parts of the laminar flow hood

A laminar flow workbench consists of the following parts:

1. Cabinet

• The cabinet is made of stainless steel with little or no gaps or joints to prevent spores from accumulating.
• The housing isolates the internal environment created within the laminar flow and protects it from the external environment.
• The front of the case features a glass shield that opens fully in some laminated cases or has two openings in some to allow the user's hands to enter the case.

2. Workplace

• Inside the cabinet there is a flat work station for all processes to be carried out.
• Culture plates, burners and handles are placed at the work station where the operation takes place.
• The countertop is also made of stainless steel to prevent rusting.

3. Filter mat/pre-filter

• At the top of the cabinet is a filter mat through which air is drawn into the cabinet.
• The filter pad prevents dust particles and some microbes from entering the working environment inside the case.

4. Fan/Blower

• A fan is located under the filter pad, which sucks in air and moves it through the housing.
• The fan also allows air to flow into the HEPA Sp filter, so any remaining microbes are caught as they pass through the filter.

5. UV-Lampe

• Some laminar flow hoods may have a germicidal UV lamp that sterilizes the cabinet interior and contents prior to operation.
• The UV lamp must be turned on 15 minutes before the operation to avoid exposing the user's body surface to UV rays.

6. Fluorescent lamp

• There is a fluorescent tube inside the cabinet to provide sufficient light during operation.

7. HEPA-Filter

• The high-efficiency particulate air filter is located inside the cabinet, making the operating environment more sterile.
• The pre-filtered air passes through the filter, which retains fungi, bacteria and other dust particles.
• The filter ensures a sterile condition inside the cabinet, reducing the chance of contamination.

Principle/mode of operation of the laminar flow hood

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• The laminar flow cabin principle is based on the laminar flow of air through the cabin.
• The device uses internal airflow through one or more HEPA filters to create a particle-free environment.
• Air is drawn in through a filter system and then expelled over the work surface as part of the laminar airflow.
• The air first flows through the filter mat or the pre-filter, which enables an optimized air flow within the housing.
• The blower or fan directs air to the HEPA filters.
• HEPA filters trap bacteria, mold and other particles so the air you expel is particle-free.
• Some of the exiting air then passes through the perforation in the bottom rear edge of the cabinet, but most of it passes through the workbench as it exits the cabinet toward the operator's face.
• The laminar flow hood is closed on the sides and a constant positive air pressure is maintained to prevent contaminated outside air from entering the cabinet.

Procedure for operating the laminar flow booth

The procedure to be followed when operating a laminar flow cabinet is given below:

1. Before operating the laminar flow cabinet, the cabinet must be inspected to ensure that there are no UV sensitive items inside the cabinet.
2. The hood glass shield is then closed and the ultraviolet light is turned on. UV light should be maintained for approximately 15 minutes to ensure countertop surface sterilization.
3. The ultraviolet light is then turned off, saving about 10 minutes of time before the airflow is turned on.
4. The air flow is switched on about 5 minutes before the start of operation.
5. Then the glass cover is opened and the fluorescent lamp is also switched on during operation.
6. To ensure better protection, the cabinet work table can be treated with other disinfectants, e.g. B. 70% alcohol sterilized.
7. After the work is completed, the air flow and the fluorescent lamp and the glass shade are closed.

Cabinet types with laminar flow

Depending on the direction of air movement, laminar flow cabins are divided into two types:

1. Vertical cabin with laminar flow

• In vertical flow cabinets, air flows from the top of the cabinet directly to the bottom of the cabinet.
• A vertical airflow hood does not require as much depth or space as a horizontal airflow hood, making it more manageable and reducing the likelihood of airflow obstruction or contaminated air moving downstream.
• The vertical laminar flow cabinet is also considered safer because it doesn't blow air directly at the person conducting the experiments.

2. Horizontal laminar flow cabinet

• With horizontal laminar flow cabinets, the ambient air comes in behind the bench, which is then blown onto the HEPA filters by the fan.
• The filtered air is then discharged horizontally into the work environment.
• An advantage of this cabinet is that the air flow parallel to the work space cleans the environment at a constant speed.
• The eluent air falls directly on the operator, which can reduce the safety level of this type of laminar flow cabinet.

Laminar flow hood used

The following are some common uses of a laminar flow cabinet in the laboratory:

1. Laminar flow cabinets are used in laboratories for contamination-sensitive processes such as plant tissue culture.
2. Other laboratory processes can be performed inside the cabinet, such as: B. preparing media plates and growing organisms.
3. The operation of particle-sensitive electronic devices is carried out inside the housing.
4. In the pharmaceutical industry, drug preparation techniques are also performed inside the cabinet to ensure a particle-free environment during operation.
5. Laminar flow cabinets can be tailor-made for some special tasks and can also be used for general laboratory techniques in the microbiological and industrial fields.

Precautions

When operating with laminar air flow, the following things must be observed:

1. The laminar flow cabin must be sterilized with UV light before and after the operation.
2. UV light and airflow should not be used at the same time.
3. Work should not be carried out when the UV light is on.
4. The operator must wear a lab coat and long gloves.
5. The workbench, glass guard and other components inside the cabinet must be sterilized before and after the work is finished.

references and sources

• Collins CH, Patricia M and Lyne JM (1995). Collins and Lynes Microbiological Methods, Seventh Edition. Grange, Butterworth, Oxford.
• 5 % – https://www.lamsys.com/products/vertical_laminar_flow/
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• 1% – https://magnaflux.eu/en/Resources/FAQs/FAQs-UV-Lâmpadas
• 1 % – https://en.wikipedia.org/wiki/Laminar_flow_cabinet
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• <1 %: https://www.sciencedirect.com/topics/immunology-and-microbiology/laminar-flow-cabinet
• <1 %: https://www.safety.rochester.edu/ih/uvlight.html
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• <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