Definition of Laminar flow
A Laminar flow cabinet or hood is an enclosed workspace that creates an environment free of contaminants by using filters to remove all particles that enter the cabinet.
They are made to shield the work from the elements and are suitable for the aseptic distribution of certain media as well as pouring plates. Laminar flow cabinets can be compared to biosafety cabinets, with the only difference being that in these flow cabinets, the air that is emitted is drawn directly into the person’s face. In a biosafety cupboard, both the user and the test sample are protected , while in a laminar flow cabinet only the sample is secured but not the user.
Principle of Laminar flow hood
The concept behind the laminar flow cabinets is built on the air flowing in a laminar manner across the cabinets. The cabinet works by utilization of an inward movement of the air over one of HEPA filters in order to produce a dust-free environment. The air passes through a filtration system , and is then expelled across the surface of the work area as component of the flow of air. The air is first pushed through the pre-filter or filter pad which allows for a smooth air flow into the cabinet.
Then, the blower or fan directs airflow towards then the HEPA filters. The HEPA filters then trap bacteria as well as fungi, and other particles so that the air that flows out of them is clean air. The effluent air is then filtered through the perforation on the bottom of the rear of the cabinet. However, the majority of it flows over the bench that is used for work, before moving from the cabinet toward the side that the user is facing. Laminar flowhood has been encased by the sides and a constant pressure of air is maintained to stop the entry of unclean external air inside the cabinet.
Components/ Parts of Laminar flow hood
A laminar flow cabinets consists of the following elements:
1. Cabinet
The cabinet is made of stainless steel and has minimal or no gaps or joints, which prevent the accumulation of the spores. The cabinet acts as an insulation for the internal environment that is created within the laminar flow. It also shields it from the external environment. The cabinet’s front is covered with the shield of glass that can be opened completely, while others have two holes for users’ hands to access the cabinet.
2. Working station
A flat workstation is located inside the cabinet for the procedures to take into consideration. Burners, culture plates and loops are set on the working area which is where the process takes place. The worktop is constructed of stainless steel in order to avoid corrosion.
3. Filter pad/ Pre-filter
Filter pads are located in the upper part of the cabinet which air can enter the cabinet. The filter pad is used to keep microbes and dust particles from entering the work environment inside the cabinet.
4. Fan/ Blower
A fan is situated under the filter pad, which absorbs air and then moves it inside the cabinet. The fan also facilitates the air to move towards the HEPA filter, which ensures that remaining microbes get trapped after moving across the.
5. UV lamp
Some laminar flow hoods could include a UV germicidal light which sterilizes the inside of the cabinet as well as its contents prior to the procedure. The UV lamp must be switched on for 15 minutes prior to the time of the operation to ensure that there is no exposure of UV radiation to the body surface of the person.
6. Fluorescent lamp
The light source is inside the cabinet in order to provide adequate lighting during operation.
7. HEPA filter
The high-efficiency particulate filter is located inside the cabinet. It makes the atmosphere more safe to ensure the smooth operation. The air that has been pre-filtered passes through the filter that traps bacteria, fungi and dust particles. The filter guarantees a clean environment inside the cabinet, which reduces the chance of contamination.
Types of laminar flow cabinet
Based on the direction in which the air moves the laminar flow cabinets are classified into two kinds:
1. Vertical laminar flow cabinet
In horizontal flow cabinet, air flows through the upper part of the cabinet toward the lower part in the cabinets. A vertical airflow bench doesn’t require as much room in the floor and depth as an airflow hood that is horizontal, that makes it easier to manage and reduces the risk of obstruction to airflow or the movement of air contaminated downstream. Vertical laminar flow cabinets is also considered to be safer since it doesn’t blow air directly toward the person conducting the tests.
Advantages
- Hood not as deep requires less area for floor
- Safety: Air does not directly hit the user, while sash acts as an obstruction between the face of the operator
- Filter on top makes it easy to access
- A less turbulent effect of the impact of air on big objects, processing machines or other equipment
- There is less cross-contamination of the items that are positioned in the workspace
- Working heights that are higher for large or tall equipment
Disadvantages
- Overhead clearance requirements for changing filters or servicing equipment may require a step-ladder
- Do not place hands or objects over other objects obstructions airflow
- A higher degree of turbulent effect from air hitting work surfaces
2. Horizontal laminar flow cabinet
In Laminar flow horizontal cabinets the air surrounding comes from behind the bench. It is carried by the blower toward HEPA filters. HEPA filters. The filtered air is discharged horizontally towards the work environment. One benefit to this kind of cabinet is airflow running parallel to the workplace cleans the surroundings at an unchanging speed. The air that is emitted directly strikes the user, which could decrease the security levels of these laminar flow cabinets.
Advantages
- Laminar airflow runs parallel to the work surface which eliminates turbulent effects of the vertical airflow that strikes perpendicularly to the work surface
- Easy to move and move sterile equipment and other materials closer to the face of the filter (upstream from any other contaminants)
- Hands and gloves generally are less likely to be contaminated since they’re just downstream of the sample
Disadvantages
- Service or filter change usually requires repositioning of the hood to allow rear access
- Large samples obstruct laminar air flow, may contaminate downstream samples
- If not sash is used it can blow smoke or powders directly into the face of the operator.
Uses of Laminar flow hood
Here are some of the most typical uses for an laminar flow cabinet the lab:
- Laminar flow cabinets are utilized in laboratories to test contamination-sensitive procedures like tissue culture of plants.
- Other lab processes such as preparation of media plates and the cultivation of organisms are carried out inside the cabinet.
- The operation of electronic devices that are sensitive to particles devices take place inside the cabinet.
- In the pharmaceutical industry the drug preparation processes are also carried out in the cabinet to guarantee that there is no dust in the processes.
- Laminar flow cabinets are customized to suit specific work, and also utilized for general laboratory techniques within the medical as as industrial sector.
Precautions
While operating the laminar flow it is important to consider the following factors: be considered
- The cabinet for laminar flow should be cleaned with UV light prior to and following the procedure.
- Airflow and UV light are not to be combined.
- There is no need to carry out while you are under the UV light is turned on.
- The worker should be attired in lab coats and gloves.
- The work bench, the glass shield and other parts inside the cabinet need to be cleaned before and after the end of the work.
How to Clean a Laminar Flow Hood
Air filtration and cleanliness are vital to maintaining the level of sterility in a cleanroom or lab as well as for the laminar airflow hood. A proper cleaning and maintenance process can yield accurate results. If the cleaning procedure is not implemented, contamination can cause your results to be unusable. Cleaning the hoods of laminar flow should be carried out regularly by every lab employee.
Follow these simple steps will ensure that your device is clean.
Cleaning Equipment
- 70% ethanol (Most effective in killing microbes) – Avoid using soap and water
- Laboratory-grade wipes
- Biohazard trashbags
- Lint-free cleanroom cloths
- Laboratory gowns or coats should be worn
- Gloves, face, and eye protection
Vertical Laminar Flow Hood Cleaning Steps
- Begin by cleaning the back of the hood of your laminar flow
- Clean the walls of the side by sweeping them between left and right, moving from top to the bottom
- Finally, wash the work area. Start at the side of the unit, and move to the front
Horizontal Laminar Flow Hood Cleaning Steps
- Begin by cleaning the ceiling of the laminar flow hood
- Clean the walls on the sides using a sweeping motion starting from the left from top to the bottom
- Finally, wash the surface of your work. Start from the side of the unit, and move to the front
Cleaning Tips
- Do not spray disinfectant directly on the HEPA filter, or get it in contact with the filter.
- Check the hood for spills or stains. If there is any you can spray the wipe with disinfectant and then clean it up.
- To clean, grab an old towel and fold it into half or quarters. There are slight variations in the process of cleaning based on the type of hood you have, whether horizontal or vertical hood.
- A new fabric should be used on every wall
- Always wash from top to bottom from all the way down to the bottom
- Overlap every swipe
- Filters should be replaced each 3 to 5 years
Do’s and Don’ts When Using Laminar Flow Cabinets
It is important to be aware of how to make use of any equipment correctly. This is not just to ensure efficient performance, but, most importantly, to attain the maximum level of security.
Watch the following video about the things you have to be aware of and what not to do when working with Laminar Flow Cabinets. Enjoy!
Do
- Always minimize clutter: Laminar flow cabinets aren’t storage cabinets. Clutter can impede the flow of laminar air around the work space. In addition, clutter makes it extremely difficult to clean the surface.
- Always clean your hands and arms prior to going into the premises: The personnel is the primary source of contamination. Touching is one of the most frequent ways of introducing bacteria into the sterile products. Hand washing properly is vitally essential as your fingers contain numerous bacterial components. Hand washing must not just be carried out prior to working at the workplace but as well after.
- Arrange objects in such a way that full benefits of the laminar flow of air can be achieved: Properly arranging all items in the laminar flow workbench provides a work area that is directly bathed with clean air from the ULPA filter.
- Do not spray or squirt solutions on the HEPA/ULPA filter: There should be no way for the solution to touch the HEPA/ULPA filter in order to prevent pollution with air that flows downstream.
- Remove wraps and outer pouches near the edge of the work space: Wraps and pouches that are outside are not sterile, which means they could introduce contaminants onto the work area. They can also be considered obstructions, and therefore they could interfere with the flow of air through the laminar air.
- Keep large objects away from the back of the hood: Large objects contaminate all the other items downstream and also disrupt the laminar airflow pattern which suspends the contaminants and removes them from the area.
- Keep coughing, quick movements, and talking to a minimum in the main work area: The activity of employees can create particles. They can disrupt the circulation of air. This could also be a source of contamination. If you must talk make sure you keep it out of the workstation.
- Always clean your surfaces prior to getting into the cabinets: Only sterile items are allowed to be put in the area that is clean. Be sure that all of your items are cleaned properly to prevent any contamination on the work area.
Don’t
- Put any waste and other items in the hood: Non-sterile and waste items cause turbulent airflows and can introduce contaminants into the clean work surface and the sample that is sterile.
- Wear jewelry on your wrists and hands: Jewelry is not sterile, which means they can introduce particles or bacteria into the work environment. They also decrease the cleanliness of hands when worn around the work area.
- Remove any items that are critical from the air source: Make sure there is a clear pathway between your filter and the place within the hood in which the procedures are being carried out. Air that is emitted from nonsterile items can be contaminated by the particles that come by these objects.
- Keep your eyes on to the filter while opening ampoules, or when adjusting the syringes: Syringes andampoules contain salt solutions, which could get deposited on the HEPA/ULPA filter. This could damage the filter.
- Introduce unnecessary objects into the work area: It is not recommended to introduce unnecessary items into the work space should be avoided as often as it is possible. The flow of traffic into a clean space should be kept to a minimum.
- Set large objects at the cabinet’s back as they can disrupt the flow of air, and can contaminate everything downstream.
- Do not use materials that have not been disinfected: Products that weren’t disinfected may cause contamination on the clean work area, thus contravening the primary function of an laminar flow cabinet that is to safeguard your equipment from contamination.
References
- http://escolifesciences.pk/news/1368/
- https://www.terrauniversal.com/blog/horizontal-vs-vertical-laminar-flow-hoods/
- https://microbenotes.com/laminar-flow-hood/
- https://www.lamsys.com/products/vertical_laminar_flow/
- https://www.laminarflows.co.uk/
- https://magnaflux.eu/en/Resources/FAQs/FAQs-UV-Lamps
- https://en.wikipedia.org/wiki/Laminar_flow_cabinet
- https://www.trane.com/residential/en/products/indoor-air-quality/cleaneffects/
- https://www.sciencedirect.com/topics/immunology-and-microbiology/laminar-flow-cabinet
- https://www.safety.rochester.edu/ih/uvlight.html
