Biosafety Cabinet Class II: Working Principle, Types, Specifications, and Buying Guide

Class II Biosafety Cabinet is an important piece of equipment in every cell culture lab, virology lab, and hospital pharmacy. You have probably been using it for thousands of times already. There are, however, many users who do not know about the working of air inside it. It is very dangerous as misuse of Biosafety Cabinet is better than no use at all. 

What Is a Class II Biosafety Cabinet? 

Class II Biosafety Cabinet is a partially enclosed and ventilated containment enclosure that protects three important things: the user, the sample, and the environment. Only few other containment enclosures can provide protection to all the three factors simultaneously. Class I provides protection to the user only by exposing the sample to room air. Class III biosafety cabinets are fully enclosed glove boxes. 

Air Flow 

The air flowing from the room enters the enclosure through the front grille, thereby preventing aerosols from reaching the face of the person working inside the cabinet. Air flowing over the top of the work bench moves down in a laminar flow after undergoing HEPA filtration. The exhaust air undergoes filtration in the second HEPA filtration unit. Since the HEPA filter eliminates 99.97% of all the particles above 0.3 microns in size, the exhaust air is cleaner than the intake air.

Simply put the laboratory notebook on the front grille, and the barrier is gone. Type A1, A2, B1, and B2 

A2 type is the one that is most commonly bought by laboratories. A2 filters around 70% of air and discharges the rest either to the room or through the thimble to the building exhaust. B2 type is completely exhausted outside, and is used for handling volatile, toxic substances and radionuclides. B1 is the type between these two. A1 is the old one with a very slow inflow rate. 

This is the way how the buyer can be fooled: It is hazardous and inconvenient to recycle chemicals above your hands by using A2 type. Seek advice from your biosafety officer before buying the PO. 

Safety Practices to Follow 

Make sure that the cabinet operates for at least five minutes before starting the work. Use only those things which you are going to use as the clutter hinders the air flow inside the cabinet. Start from the cleanest and move on to the dirtiest. Move your hands slowly in a straight line inside and out of the sash. 

Do not use the Bunsen burner as it causes interference in the downward movement of air due to the plume of heat generated by the flame. You can use either disposable loops or bacti-cinerator for your experiment. 

The surfaces need to be cleaned before and after using the cabinet with 70 percent ethanol. If there is any spillage, you need to clean it with bleach and wash it with water to prevent the corrosion of stainless steel surface. 

Certification and Maintenance 

The hood needs annual certification for NSF/ANSI 49, as well as any time it is moved. Technologists test the inflow rate, downflow, and filters. This is one extremely costly metallic machine that does not even function without certification. Too strong? Well, from personal experience, labs have identified six months' worth of contamination problem due to the non-certification of the old filter for three years. 

Conclusion 

Except in a few circumstances regarding specific chemicals where it cannot be used, always use type A2. Ensure that all personnel are certified, particularly the new personnel. No need for certification. Biosafety Cabinet Class II is as good as the person using it.

The surfaces need to be cleaned using 70% ethanol before and after the usage of the cabinet. In case of spillage, then first clean it using bleach and then wash with water to prevent rusting of the stainless steel surface.