Many labs have received notices this year that their Biological Safety Cabinet (BSC) certification company will no longer certify a certain type of BSC that those labs have had for years. NSF International (formerly the National Sanitation Foundation) is an organization that supplies product testing, inspection and certification. NSF is accredited by the American National Standards Institute (ANSI) to develop American National Standards, and in 2010 an updated version of the NSF/ANSI 49 was published. This is better known as the Biosafety Cabinetry: Design, Construction, Performance, and Field Certification standard.
The names can be confusing, but the important message is the revisions to the standard eliminated the option of direct-connected Type A cabinets (which had been previously allowed). Also, an alarm requirement was added for canopy connected Type A cabinets. There was time allowed for sites with these types of BSCs to make necessary adjustments, and in 2016 field certification agencies have been told they can no longer certify BSCs which do not meet the updated standards.
That means that some labs that have not updated their BSCs or purchased new ones, they are left with uncertified (and therefore unusable) cabinets.
There are three main classes of BSCs. Class I offers the least amount of protection, and it pulls air in and over the work area. The air is then exhausted via a HEPA filter. Class II BSCs are the most commonly-used cabinets in clinical laboratories. They offer a maintained inward airflow, a HEPA-filtered unidirectional airflow within the work area, and a HEPA-filtered exhaust into the room or to the facility exhaust system. Class III BSCs (or glove boxes) are for use with high risk biological agents, and they are typically sealed and gas-tight enclosures.
The commonly-used class II cabinets come in a variety of designs or types:
- A1 – 70% of the air recirculates through the supply HEPA filter, the other 30% of air goes through the exhaust HEPA filter.
- A2 – 70% of the air is recirculated through the supply HEPA filter, the other 30% of air goes through the exhaust HEPA filter. The air intake is faster than in a type A1 cabinet.
- B1 – 40% of the air is recirculated, 60% of air is exhausted.
- B2 – No air is recirculated within, it is all exhausted into the facility system.
Some older Class II Type A cabinets had the exhaust directly connected to the facility exhaust system. This is no longer permitted since hard connections need to meet specific regulated criteria and is not considered the safest type of connection. If connected to an exhaust system, the cabinets must use a canopy (thimble or air-gap) connection which has an opening to the room. Because there is always the potential for equipment failure (and a possibility of air contamination to the room via the opening), an alarm system must also now be in place to alert the user of this possible danger. In 2016, all BSC field service workers were notified not to certify Type A cabinets with a hard connection or with a non-alarmed canopy connection. If you received a memo and had an issue with certification this year, that’s why!
No matter what Class II type of BSC you are using, there are some basic safety guidelines every user should know in order to keep protected while working. If the blower is not kept on all the time, turn it on about ten minutes before use. This will stabilize the protective air flow in the cabinet. Adjust the seat height so that the user’s face is above the front opening. Set all specimens and materials that are needed inside the work space, and separate the clean from the dirty. Do not set anything on the front grille. Objects too close to the front, side, and rear air grilles can disturb airflow and compromise the specimen and the worker’s safety.
When working in a BSC, avoid frequent and fast motions. When moving arms in and out of BSC, move them slowly and perpendicular to the sash. This will allow less interference with the air flow. Be sure to limit traffic in the area when working- people walking behind a BSC in use will disturb the air flow such that air will pass out of the cabinet into the breathing zone of the user. In general, fume hoods and BSCs should never be located in high traffic areas.
Once work is completed inside the BSC, properly dispose of all waste material. Disinfect the cabinet surfaces using an extension apparatus to reach the back wall. Never put your head inside the BSC. Use a bleach solution for disinfection. If damage to the surface is a concern, wipe down the surface with water after using the bleach. Let the BSC run for at least 10 minutes before turning off.
It is important to remember that a Biological Safety Cabinet is an engineering control designed to protect the worker, but it only does so if used properly. Make sure all users are properly trained to use a BSC safely. Have them certified annually, and let certified professionals perform the required maintenance. If you received a memo this year, it may be time to purchase a newer BSC in order to maintain safe work practices in your lab. Ask your field service representatives for the best option for your laboratory.
-Dan Scungio, MT(ASCP), SLS, CQA (ASQ) has over 25 years experience as a certified medical technologist. Today he is the Laboratory Safety Officer for Sentara Healthcare, a system of seven hospitals and over 20 laboratories and draw sites in the Tidewater area of Virginia. He is also known as Dan the Lab Safety Man, a lab safety consultant, educator, and trainer.