What are Biological Safety Cabinets?

Biological safety cabinets are wonderful and important tools when working with pathogens. However, they can be pretty confusing to figure out. Between the various different Classes and Biosafety Levels, it often feels like an overwhelming task to try and figure out which kind of cabinet you need for your particular applications. But knowing the differences is vital to your safety, the accuracy of your tests, and the health of the environment.

The National Sanitation Foundation (NSF) is responsible for testing and classifying biological safety cabinets. The NSF and The American National Standards Institute (ANSI) jointly set standards for the various classes and types of biological safety cabinets which are outlined in great detail in the NSF/ANSI 49-2016 Biosafety Cabinetry: Design, Construction, Performance and Field Certification.

Below, we'll review the basics of each of the three classes of biological safety cabinets, the biosafety levels (BSL) covered by each, and how AirClean Systems can help you find the right match for your lab. To get in-depth information on the different biosafety levels and what they mean, read through the CDC's Quick Learn Lesson on Recognizing the Biosafety Levels.

Class I - Biosafety Levels 1, 2, 3, and 4 (Positive pressure containment suit required for use in BSL 4)

First is the most basic of all the biological safety cabinets: Class I. These cabinets are to be used exclusively for operator and environmental protection.

They protect the operator by moving air away from the technician and into the cabinet. In this way, they keep any contaminants from exiting in the direction of the user. Since air from the surrounding lab is pulled over the sample in a Class I, there is no protection for the sample from potential contaminants in the lab.

Class I cabinets are also designed to protect the environment from the specimens being worked on within them. All the air that is drawn into the cabinet is HEPA filtered before being exhausted back into the room. The HEPA filtration prevents particulate and pathogens from escaping the cabinet and contaminating the environment.

Class I biological safety cabinets are best used with biological agents which pose a low to moderate risk. The majority of routine applications, like pipetting, can be done within a Class I biological safety cabinet, like the AC600 Series UPUV Class 1 Biological Safety Workstation.

Class II - Biosafety Levels 1, 2, 3, and 4 (Positive pressure containment suit required for use in BSL 4)

Next comes the mid-range biological safety cabinet: Class II. Basically, Class II cabinets are to be used for simultaneous operator, process, and environmental protection.

They function similarly to Class I cabinets in order to protect the operator and environment by keeping air flowing away from the operator and passing it through a HEPA filter before releasing it into the environment. However, Class II cabinets also function to protect the process or specimen being worked on from contamination. This is done by ensuring that the air which enters the workspace within the cabinet is also HEPA-filtered, keeping any airborne pollutants from contaminating samples.

This is where things start to get a bit more complex. Within the Class II family are five subcategories: A1, A2, B1, B2, and C1.

A1 and A2 are nearly identical with a few distinctions. A1 has a minimum inflow velocity of 75 feet per minute while A2 has a minimum inflow velocity of 100 feet per minute. Additionally, A1's contaminated ducts and plenums are under positive pressure while A2 is under negative pressure.

B1 and B2 are similar in that they both must be hard connected to a building's exhaust system and in that their plenums are both under negative pressure. One difference is that in the B1, 30% of the air drawn into the cabinet is HEPA-filtered and then recirculated within the cabinet, while in B2, all of the air is expelled from the cabinet after HEPA filtration. This makes B2 more expensive to run, but safer when dealing with more hazardous pathogens.

Lastly, there is Type C1. Type C1 is similar to a B1 as far as the air flow pattern is concerned, however, unlike a B1, a C1 contains its own blower to circulate the exhaust air through a HEPA filter and back into the room.

Class II biological safety cabinets are best used with biological agents which pose a low to moderate risk.

Class III - Biosafety Level 1, 2, 3, and 4

Finally comes the heavy hitter in the world of biological safety cabinets: Class III. Often called "gloveboxes", Class III cabinets are meant to protect the operator, process, and environment to a much higher degree than a Class II cabinet, but the highest priority is ensuring the safety of the operator and environment.

Class III biological safety cabinets completely encase the specimen being worked on in an airtight chamber. The operator can only manipulate the specimen via gloves built in to the sealed front window of the cabinet, thus the nickname, "glovebox." This arrangement ensures that whatever specimen is being worked on cannot accidentally come into contact with or infect the operator.

Class III biological safety cabinets are best used with biological agents which pose a high risk and where the absolute maximum protection is required.

What Do You Need?

Wading through all the terminology and requirements to find the right biological safety cabinet doesn't have to be as hard as it may seem. Contact AirClean Systems at 919-255-3220 and one of our qualified staff will be happy to help you find the biological safety cabinet that meets your needs.