Laminar Air Flow Working Principle

Laminar Air Flow

A laminar air flow is a piece of equipment that is generally used in microbiology laboratories. It consists of a chamber with an air blower attached to its rear side that allows the flow of air with a uniform velocity in straight lines that are parallel to each other. The main purpose of a laminar flow cabinet/hood is to form a contaminant-free work environment. For this purpose, it filters and captures all types of impurity particles entering the cabinet. It makes use of a filter pad and a special filter system known as a high-efficiency particulate air filter or HEPA filter, which can remove the airborne impurity particles that are up to 0.3 micrometres in size. A laminar air flow chamber is also known as a laminar flow closet or a tissue culture hood.

Working Principle of a Laminar Air Flow Chamber

As the name itself suggests, the laminar air flow chamber works on the principle of laminar flow of air. The flow of air is said to be laminar in nature if the gas molecules travel in multiple straight lines that are parallel to each other. The gas molecules do not get mixed up with each other while travelling. It makes use of a high-efficiency particulate airflow system that tends to capture and eliminate all sorts of airborne impurity particles to maintain a clean and sterile environment.

Parts of a Laminar Air Flow Chamber

1. Cabinet

The cabinet of the laminar air flow chamber is typically made up of stainless steel. It provides insulation to the sterile environment created inside the laminar air flow hood and protects it from the contamination and impurity particles present outside. The front side of the cabinet consists of a glass shield that allows the user to access the cabinet by providing a partial or complete opening.

2. Working Station 

A flat working station is present inside the chamber that provides a solid base to carry out processes such as plant tissue culture, electronic wafer formation, the culture of microorganisms, etc. It helps to hold the culture plates, burners, samples and other tools in place. The material generally used to manufacture the laminar air flow chamber working station is stainless steel. This is because stainless steel is robust in nature and does not undergo rusting or corrosion easily.

3. Filter Pad

The filter pad is used to block or capture the impurity particles and prohibit them from being transmitted any further. The filter pad is also known as the prefilter or the primary filter as it initially sucks the air and performs the first stage filtering of air. In a vertical laminar air flow cabinet, a filter pad is placed on the top of the device; whereas, in the case of a horizontal laminar air flow cabinet, it is fixed at the bottom of the chamber. Impurity particles of size 5 microns or higher typically get trapped by a filter pad.

4. Fan or Blower

The fan or the blower sucks the pre-filtered air through the filter pad and transmits it towards the high-efficiency particulate air filter. In a vertical laminar air flow cabinet, the blower is usually present right below the filter pad. On the contrary, the position of the fan or blower in the case of a horizontal laminar air flow cabinet is right next to the filter pad.

5. HEPA Filter

Hepa filter or high-efficiency particulate air filter is a special air filter present inside the chamber that helps in the removal of all sorts of contamination particles including bacteria, fungi, and dust particles to maintain a safe and sterile environment. For this purpose, the pre-filtered air is made to pass through the HEPA filter, which acts as the secondary or final filter. The particles that are even 0.3 microns in size can be successfully eliminated with the help of a HEPA filter. To remove the impurity particles, a HEPA filter generally makes use of three mechanisms as given below:

1. Interception

Under this mechanism, the impurity particles get stick to the filter fibres. The interception mechanism is used by the HEPA filter to filter out large impurity particles.

2. Impaction

It involves a sudden change in the airflow that causes the particles to get embedded in the filter fibres. The impaction mechanism is also used to remove comparatively larger impurity particles from the inner environment of the chamber.

3. Diffusion

Here, the impurity particles tend to interact with each other, move in a zig-zag path, and display Brownian motion. This random and repeated motion of the particles causes them to get trapped within the filter fibres. Relatively smaller contaminant particles can be eliminated with the help of the diffusion process.

6. UV Lamp

A laminar air flow chamber necessarily consists of an ultraviolet light lamp, which is generally used to kill the germs and bacterias that are invisible to the naked eye. The chamber must be thoroughly exposed to ultraviolet radiation before and after use. The UV lamp purifies the chamber as well as all the other pieces of equipment present inside it including Petri dishes, test tubes, beakers, watch glasses, etc. The UV lamp should be turned on at least 15 minutes before the operation.

7. Fluorescent Lamp  

The main purpose of a fluorescent lamp in a laminar air flow chamber is to produce proper illumination and lightning inside the hood.

Parts of a Laminar Air Flow Chamber

Working of a Laminar Air Flow Chamber

When the device is turned on, the blower and the fluorescence light get activated. The air gets sucked in through the blower, the larger impurity particles get eliminated by the filter pad, while the smaller contaminants are removed with the help of the HEPA filter. After some time, the lid of the device is opened completely or partially. The workstation is then thoroughly and properly wiped with the help of alcohol and a clean fabric cloth or cotton. The alcohol used for this purpose can be 60-95% pure in nature. After this, the lid of the device is shut down, the blower is turned off, and the UV light is turned on. The UV light is carcinogenic in nature and causes mutations in the body thereby, causing cancer. Hence, the user must not stay for a longer duration in exposure to ultraviolet radiation. The UV light is turned on for at least 15 minutes. This kills the bacterias, pathogens, and other micro-level impurities. The UV light lamp is then turned off and the device gets thoroughly sterilized.

Working Principle of a Laminar Air Flow Chamber

Types of a Laminar Air Flow Chamber

A laminar air flow system can be broadly classified into three categories:

1. Vertical Laminar Air Flow Chamber

A vertical laminar air flow chamber consists of a fan that is fixed to the roof of the cabinet. The air is sucked in by the fan and is directed downwards in a vertical direction. The air moves from the top of the cabinet towards the bottom of the cabinet thereby, undergoing a positive pressure. Since the air does not get blown directly towards the user, it is considered to be comparatively safer. The limitation of a vertical laminar air flow chamber is that it requires double installation of HEPA filters hence, is comparatively expensive. It is widely used in laboratories.

Vertical Laminar Air Flow Chamber

2. Horizontal Laminar Air Flow Chamber

The input air enters from behind the laminar flow bench, gets sucked in with the help of the blower, and is passed through the HEPA filter. Finally, the filtered air is circulated inside the chamber in a horizontal direction. Horizontal laminar air flow chambers are bulky and need a comparatively larger surface area. Also, this type of air flow system fails to provide security to the user while handling certain drugs such as anti-neoplastic drugs as the waste air directly blows towards the user. This is the reason why vertical laminar air flow systems are generally preferred over horizontal laminar flow systems.

Horizontal Laminar Air Flow Chamber

3. Wall to Floor Air Flow System

The air after filtration enters the chamber through the lateral walls and get directed towards the floor following an inclined path. A wall to floor air flow system tends to provide a highly sterile and pure environment and is portable in nature. The only limitation to using this type of air flow system is the high installation and maintenance cost.

Advantages of a Laminar Air Flow Chamber

1. The laminar air flow devices are advantageous as they do not release any toxic gases into the environment hence, are eco friendly.

2. Laminar air flow chambers do not require frequent maintenance and repair. The only cost associated with such devices is the installation cost. Hence, they are comparatively inexpensive and economical.

3. They are easily portable and can be transported to new locations with ease.

4. Laminar air flow cabinets reduce the chances of potential turbulence in the environment during an experiment.

5. Some of the laminar air flow devices are well equipped with smart security systems that tend to raise alarms and notify the user in case of any safety breach.

Disadvantages of a Laminar Air Flow Chamber

1. Placing objects or hands on the device disrupts the air flow, causes turbulence, and reduces the ability of the device to properly sterilize the internal environment.

2. Some types of laminar air flow devices tend to blow fumes towards the users face.

3. The laminar air flow devices require proper handling and care for better operation.

Applications of a Laminar Air Flow Chamber 

A laminar air flow chamber has multiple uses in a variety of sectors including medicine, biology laboratories, chemical industries, manufacturing factories, pharmaceutical firms, and many more. Some of the prominent uses of a laminar air flow cabinet are listed below:

1. A laminar air flow cabinet is generally used in laboratories to form a sterilized environment for processes such as plant tissue culture. This is because these processes get easily affected due to the presence of impurity particles in the surroundings.

2. Manufacturing and operation of certain particle sensitive electron devices takes place inside the air flow chambers.

3. One of the prime applications of a laminar air flow chamber lies in the pharmaceutical industry. The preparation of drugs and medicines necessarily requires a clean and sterile environment. Thus, such processes are carried out inside the laminar air flow cabinets.

4. Various laboratory procedures such as media plate preparation, the culture of microorganisms, etc. are carried out inside the laminar air flow devices.

Measures to Opt while using a Laminar Air Flow Chamber 

There are certain measures that one must keep in mind while accessing or working on a laminar air flow chamber. Some of the precautions and safety measures to be followed by the user are listed as follows:

1. The operator must wear safety goggles, long gloves, and a laboratory coat while operating the device.

2. All the components and devices present inside the cabinet must be sterilized before and after use.

3. The UV light and airflow must not be used simultaneously.

4. The laminar air flow cabinet needs to be thoroughly irradiated with UV light before and after use. This helps to prohibit the growth of bacterias and foreign particles inside the device thereby, ensuring a proper sterile environment.

5. Any sort of ongoing process should be immediately terminated while the UV light is still on.

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