Laminar airflow Cabinet(hood) and biosafety cabinet(hood) appear to be one and the same but there are many differences between these two cabinets. Both of these cabinets are intended to give protection to the user and the environment at different levels.
Let's understand the major function differences and types of these two cabinets.
Laminar Airflow Cabinet
A laminar airflow cabinet is an enclosed unit that creates a microbial free environment.This microbial free environment is created by high efficiency particulate air filters which are popularly known as HEPA filters.These HEPA filters capture all the airborne particles that enter the cabinet. The pore size of HEPA filter is usually 0.3 microns which can retain bacteria, fungal spores and other particles.HEPA filters are constructed in a way that the air reaching out to the filter is passed through two more filters in order to remove the particles that are larger than 0.3 microns.
There are two types of laminar airflow cabinets based on the direction of the airflow
1. Vertical laminar airflow cabinet
2. Horizontal laminar airflow cabinet.
• In the vertical laminar airflow air moves from the top of the cabinet towards the workbench.
• Likewise in the horizontal laminar airflow the air flows from the behind towards the operator.
WORKING PRINCIPLE OF LAMINAR AIR FLOW CABINET
The air from the surrounding environment is pulled by the blower and released into the working area through the HEPA filters. From the workbench most of the air is moved towards the face of the operator and then back to the environment.
• The laminar airflow cabinets provide a unidirectional airflow with fixed velocity and pressure.
• The pressure inside the cabinet does not allow the external air entering the cabinet.
• Some laminar airflow units are equipped with UV light to sterilize the interior surfaces and components before the operation.
• The laminar airflow cabinets are used for culturing of non-infectious organisms as they do not provide protection to the operator.
Unlike the laminar airflow cabinets the biosafety cabinets not only give protection to the sample but they also protect the operator and the surrounding environment.
Based on the level of protection biosafety cabinets are classified into three classes -
CLASS 1 BIOSAFETY CABINETS
• Class 1 biosafety cabinets provide only the operator and environment safety. They do not provide product safety that is being handled.
• The class 1 biosafety cabinets pull the surrounding air from the operator side. The air inside takes the particles away from the operator and then pass through the HEPA filter before it is discharged into the environment.
• In this case the surrounding air is coming in direct contact with the product on the work surface and therefore increasing the risk of product contamination.
• In this way the class 1 biosafety cabinets protect the operator and the environment but not the product.
CLASS 2 BIOSAFETY CABINETS
• In The class 2 biosafety cabinets the air enters into the cabinet through the front grille.
• In the laminar airflow the airflow is towards the operator whereas in this case the air is pulled from the front grille. Which means the dirty air is pulled from the operator side and thus providing safety to the operator.
• The contaminated air is then pushed below the workbench and taken upwards to the plenum. From the plenum the air is passed through the HEPA filter.
• Usually 30% of the air will be sent back to the environment through the HEPA filter the remaining 70% of the air passes through another hepa filter and enters the working surface of the cabinet.
The class 2 biosafety cabinets provide the following
• a front opening with continuous inward airflow
• HEPA filtered vertical and unidirectional airflow on the working surface
• HEPA filtered air to the surrounding area
Depending on the exhaust system the airflow velocity and airflow rate the class 2 biosafety cabinets are further classified as
type A1 A2 type B1 and B2.
• The most widely used cabinets are belong to the type A2 of class 2 Biosafety cabinets.
CLASS 3 BIOSAFETY CABINETS
• The class 3 biosafety cabinets are totally enclosed containers and provided with two gloves attached to the system to perform operations.
• Hence these cabinets are also called as glove boxes the inflow and outflow of air occurs through HEPA filters.
• These cabinets are also equipped with a transfer cabinet that allows sterilization of material before they leave the glove box.