What is Laminar Airflow?
A laminar air flow is a piece of equipment that is commonly found in microbiology laboratories. It consists of a chamber with an air blower attached to the back side that allows uniform velocity air flow in straight lines parallel to each other. A laminar flow cabinet’s primary function is to create a contaminant-free work environment.
It filters and captures all types of impurity particles that enter the cabinet for this purpose. It employs a filter pad and a special filter system known as a high-efficiency particulate air filter, or HEPA filter, to remove airborne impurity particles as small as 0.3 micrometers.
Working Principle of Laminar Airflow:
The laminar air flow chamber operates on the principle of laminar air flow. If the gas molecules travel in multiple parallel straight lines, the flow of air is said to be laminar. The gas molecules do not collide while traveling. It employs a high-efficiency particulate airflow system that captures and eliminates all types of airborne impure particles in order to maintain a clean and sterile environment.
ISO 14644 specifies the approved air flow speed limits in Laminar Flow systems. This standard basically specifies that to obtain accurate Laminar Flow, the air flow speed needs to be 0.45 m/s within a 20 cm distance of the HEPA Filter’s surface (With a 20 % tolerance so minimum flow of 0.36 m/s and a maximum of 0.54 m/s).
Types of Laminar Air flow Chambers:
1.Vertical Laminar Airflow Chambers:
A vertical laminar air flow chamber is made up of a fan that is attached to the cabinet’s roof. The fan draws in air and directs it downward in a vertical direction. Positive pressure is created as the air moves from the top of the cabinet to the bottom of the cabinet. Because the air is not blown directly at the user, it is considered relatively safe.
2. Horizontal Laminar Air flow Chambers:
In horizontal laminar airflow chambers, the blower draws in the input air from behind the laminar flow bench, which is then passed through the HEPA filter. Finally, the filtered air is circulated horizontally within the chamber. Horizontal laminar air flow chambers are large and require a large surface area. Furthermore, because the waste air directly blows towards the user, this type of air flow system fails to provide security to the user when handling certain drugs, such as anti-neoplastic drugs. This is why vertical laminar air flow systems are preferred over horizontal laminar air flow systems.
Parts of Laminar Airflow Cabinet:
Stainless steel (SS 304/316/316L) is commonly used for the cabinet of the laminar air flow chamber. The cabinet’s front side is made up of a glass shield that allows the user to access the cabinet by providing partial or complete opening. It insulates the sterile environment and protects it from outside contamination and impure particles.
2. Working Station:
Inside the chamber, a flat working station provides a solid foundation for processes such as plant tissue culture, electronic wafer formation, microorganism culture, and so on. It aids in the retention of culture plates, burners, samples, and other tools. Stainless steel is commonly used in the construction of the laminar air flow chamber working station. This is due to the fact that stainless steel is resistant to rusting and corrosion.
The filter pad is used to capture or block impure particles and prevent them from being transmitted further. The filter pad is also known as the prefilter or the primary filter because it sucks in air and filters it in the first stage. A filter pad is attached to the top of a vertical laminar air flow cabinet, whereas it is attached to the bottom of a horizontal laminar air flow cabinet. Impure particles of 5 microns or larger are typically trapped by a filter pad.
4. Fan or Blower
The blower or fan draws pre-filtered air through the filter pad and directs it to the high-efficiency particulate air filter. The blower is typically located directly beneath the filter pad in a vertical laminar air flow cabinet. In the case of a horizontal laminar air flow cabinet, the fan or blower is located right next to the filter pad.
5. HEPA filter:
HEPA filters are special air filters found inside chambers that aid in the removal of contamination particles such as bacteria, fungi, and dust particles. HEPA filter conforms to EU-14 Grade at supply position with an efficiency rating better than 99.999% / 99.997% for 0.3 microns. Pre-filtered air is forced through the HEPA filter, which serves as the secondary or final filter. HEPA filters typically employ three mechanisms to remove impure particles, as detailed below:
6. UV lamp:
A laminar air flow chamber must have an ultraviolet light lamp, which is used to kill germs and bacteria that are invisible to the naked eye. Before and after use, the chamber must be thoroughly exposed to ultraviolet radiation. The UV lamp cleans the chamber as well as all of the other equipment inside it, such as Petri dishes, test tubes, beakers, and watch glasses. The UV lamp should be activated at least 15 minutes before the procedure.
7. Fluorescent lamp:
The primary function of a fluorescent lamp in a laminar air flow chamber is to provide adequate illumination and lighting within the hood.
Laminar flow equipment, such as laminar flow hoods and chemical fume hoods, are used in pharmacies and laboratories to reduce the risk of contamination to the worker or the specimen.
In the case of a compounding pharmacy, the “specimen” could be a dangerous drug. In other laboratories, the specimen could be infectious particles, bacteria and viruses, unicellular and multicellular organisms, potentially hazardous substances requiring work in laminar flow protection devices.
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