Introduction to Biological Safety Cabinets

The need to protect personnel, product, and the environment from exposure to biohazards and cross contamination during routine procedures has never been more acute. The Baker Company has developed a wide variety of biological safety cabinets designed to meet diverse applications in the life science, clinical, pharmaceutical and industrial laboratory.

Superior Environmental Protection

Because of the critical nature of such laboratory work, Baker products are designed and manufactured to meet specific needs of the workplace, and to operate within a performance envelope which guarantees the widest margin of safety and product protection for the most demanding laboratory conditions.

Baker encourages you to learn as much as possible about the capabilities, limitations and appropriate use of specific biosafety cabinets. The adequacy of any containment cabinet for the user’s personal safety should be confirmed by an industrial hygienist or qualified safety officer.

We invite questions and comments by telephone, from our web site, or during personal visits to our manufacturing facility and research laboratories.

Cabinet Purpose

In varying degrees, a laminar flow biological safety cabinet is designed to provide three basic types of protection:

  • Personnel protection from harmful agents inside the cabinet.
  • Product protection to avoid contamination of the work, experiment, or process.
  • Environmental protection from contaminants contained within the cabinet. 

How Biological Safety Cabinets Are Classified

Classification is an important consideration in the selection of any biological safety cabinet. Over the years, the scientific community has adopted commonly accepted classification criteria to differentiate containment capabilities and performance attributes. Biological safety cabinets are divided into three classifications. Baker designs and manufactures all of these types of biosafety containment cabinets.

Classification

Biosafety Level

Application

Class I 1, 2, 3 low to moderate risk biological agents
Class II 1, 2, 3 low to moderate risk biological agents
Class III 4 high risk biological agents


NSF International (The National Sanitation Foundation) conducts tests on biological safety cabinets to ensure that products achieve minimum standards for cabinet classifications, as devised by NSF. Those standards are defined within NSF/ANSI 49 - 2008, Biosafety Cabinetry: Design, Construction, Performance, and Field Certification.

  • NSF Standards are reviewed every five years.
  • Tests are conducted on cabinets submitted to NSF by the manufacturers.
  • Products which meet these standards are certified by NSF.
  • Tests on cabinets are repeated every five years.

Cabinets are also required to pass field certification by an independent organization. NSF has established the standards for field tests which define the methods and acceptance criteria that are appropriately applied for determining qualification for field certification of all Class II biological safety cabinets. These field certification procedures are intended to confirm that an installed cabinet evaluated under the current version of the Standard has met all design criteria contained in NSF/ANSI 49.

Class I - Personnel and Environmental Protection Only

The Class I biological safety cabinet is designed to provide personnel and environmental protection only.

  • A Class I cabinet does not protect the product from contamination because dirty room air constantly enters the cabinet front to flow across the work surface.
  • As a partial containment unit, the Class I cabinet is suitable for work involving low to moderate risk agents (biosafety levels 1,2 and 3) where there is a need for containment, but not for product protection.
  • Unlike conventional fume hoods, the HEPA filter in the Class I cabinet protects the environment by filtering air before it is exhausted.
  • Personnel protection is made possible by constant movement of air into the cabinet and away from the user.

Class II - Product, Personnel and Environmental Protection

The Baker Company is internationally recognized for its research and development of Class II products, and offers a complete line of BSC products.

A Class II cabinet must meet requirements for the protection of product, personnel and the environment. This type of cabinet is widely used in clinical, hospital, life science, research and pharmaceutical laboratories.

In general, cabinets are classified according to the method by which air volumes are recirculated or exhausted.

The Class II biological safety cabinet has three key features:

  • A front access opening with carefully maintained inward airflow.
  • HEPA-filtered, vertical, unidirectional airflow within the work area.
  • HEPA-filtered exhaust air to the room or exhaust to a facility exhaust system.

Vertical, unidirectional airflow and a front access opening are common to most Class II cabinets. But, because Class II designs permit different airflow patterns, velocities, HEPA air filter position, ventilation rates and exhaust methods, a sub-classification of Type is needed to differentiate Class II BSC designs.

In 2002, NSF restructured the Class II classification system to reflect specific performance and installation attributes.

New NSF Classification of 2002

Cabinets previously classified as Class II, Type A/B3 are now classified as Class II, Type A2. These biosafety cabinets may be exhausted to the room, or connected to a facility exhaust system via a "canopy" connection (NSF recommends a canopy connection for cabinets exhausted to the outdoors). The Class II, Type B3 classification no longer exists for new units.

It is important to understand differences in cabinet Type in order to select the proper cabinet for your application.

 

New NSF Classification, Adopted 2002 Previous NSF Classification General Description
A1 Class II, Type A
  • 70% air recirculated; 30% exhausted from a common plenum to the room;
  • 75FPM intake;
  • may have biologically contaminated positive pressure plenum
A2 Class II, Type A/B3
  • 70% air recirculated; 30% exhausted from a common plenum to the room;
  • 100FPM intake;
  • biologically contaminated plenum under negative pressure or surrounded by negative pressure
A2 Class II, Type B3
  • 70% air recirculated; 30% exhausted from a common plenum to a facility exhaust system;
  • 100FPM intake;
  • biologically contaminated plenum under negative pressure or surrounded by negative pressure
B1 Class II, Type B1
  • 40% air recirculated; 60% exhausted from cabinet;
  • exhaust air pulled through dedicated exhaust duct into facility exhaust system;
  • 100FPM intake
  • all biologically contaminated plenums are negative to the room or surrounded by negative pressure plenums
B2 Class II, Type B2
  • 0% air recirculated; 100% exhausted from cabinet
  • exhaust air pulled through dedicated exhaust duct into facility exhaust system;
  • 100FPM intake
  • all ducts and plenums are under negative pressure
  • all contaminated ducts are under negative pressure or surrounded by directly exhausted negative pressure ducts or plenums

Note: All Baker biological safety cabinets provide containment and protection from airborne particulates for personnel, the work area, and the environment. Depending on the Type and nature of the exhaust configuration, and whether the exhaust system is treated or untreated, this containment and protection can extend to vapors and gases as well.

Class II Protection From Particulates From Vapors and Gases

Type A1
Type A2

personnel, work area (products) and environment if exhausted to room: none; not for use with vapors and gases
if exhausted to facility exhaust system, protects personnel 
if exhausted to a treated facility exhaust system protects personnel, the work area and the environment
Type B1 personnel, work area (products) and environment offers more protection to personnel and the work area the closer the vapor source is located toward rear of work area; (offers protection to the environment if exhausted to treated system)
Type B2 personnel, work area (products) and environment offers protection to personnel; (offers protection to environment if exhausted to treated system)

Biological safety cabinets can be differentiated by a variety of design and performance factors. These include face velocity, air recirculation proportion, contaminated plenum pressure and exhaust function.

Class II, Type A1 and Type A2 Biological Safety Cabinet

HEPA-filtered exhaust air in the Type A1 and A2 cabinet may be recirculated into the room or exhausted to the outdoors through a canopy exhaust connection.

  • Offers product, personnel and environmental protection.
  • Minimum intake air velocity:
    • Type A1 - 75 FPM;
    • Type A2 - 100 FPM.
  • HEPA-filtered downflow air is a portion of mixed downflow and inflow air from a common plenum.
  • Biologically contaminated ducts and plenums:
    • Type A1 under positive pressure to the room
    • Type A2 under negative pressure or surrounded by negative pressure

Class II, Type B3 Cabinet

The Class II, Type B3 classification has been eliminated by NSF. This cabinet is now called a Type A2 ducted to the outside..

Class II, Type B1 Cabinet

By definition, the Baker Company Model NCB-C® Class II, Type B1 cabinet meets the ventilation design characteristics established by the National Cancer Institute (NCI) for a General Purpose Clean Air Biological Safety Cabinet (Class II, Type B Safety Cabinet, 6 July 1976). The Baker NCB-C Class II, Type B1 exceeds the NSF Standard with unique design and features offering significant advantages in both particulate and gas/vapor containment.

  • Offers products, personnel and environmental protection.
  • The cabinet exhausts approximately 60% of the circulated air through a HEPA exhaust filter.
  • The remaining 40% of the air is recirculated to the work area through a HEPA supply filter.
  • HEPA-filtered downflow air comprised of uncontaminated recirculated inflow air.
  • Minimum intake air velocity of 100 FPM.
  • Exhausts most of contaminated downflow air through a dedicated duct exhausted to the outside after passing through a HEPA filter.
  • All biologically contaminated ducts and plenums are under negative pressure or surrounded by negative pressure ducts and plenums.
  • Type B1 cabinets must be hard connected to an exhaust system.

Baker NCB-C Surpasses Class II, Type B1 Criteria

Biosafety Cabinets with Unique HEPA Air Filtration

Baker has developed the Model NCB-C® to exceed typical Class II, Type B1 criteria, with unique design features proven to enhance containment while inhibiting cross contamination and exposure to chemicals, vapors and gases.

  • All exhaust air is removed directly from the work area (direct exhaust) and pulled through a dedicated exhaust duct into the facility’s separate exhaust system.
  • Vapors and gases emitted from vessels or work behind the air split (approximately half way back from the cabinet front) are removed and not recirculated.
  • Dual HEPA supply filters assure that all positive pressure areas are free of particulate contamination. Recirculated air is HEPA-filtered immediately below the work surface before it is passed through a HEPA supply filter above the work area.
  • In accordance with the NCI specification, unfiltered air in the Baker NCB-C® cabinet flows under negative pressure in dedicated ducts.

Approximately 40% of the descending air is pulled forward where it mixes with room air entering the perforated front grille. This air passes through the HEPA supply filter directly below the work surface, then is circulated under positive pressure through a duct to the top of the cabinet, then through another HEPA supply filter, where the process is repeated.

Class II, Type B2

Class II, Type B2 cabinets are total exhaust cabinets, widely used in toxicology laboratories and similar applications where chemical effluent is present and clean air is essential.

  • There is no recirculation within the work area.
  • Room air enters through a blower/motor in the top of the cabinet and passes through a HEPA supply filter into the work area as the vertical unidirectional airflow.
  • Descending air is pulled through the base of the cabinet through the perforated front and rear grilles.
  • Simultaneously, air entering through the perforated front opening is pulled through the grille and exhausted immediately.
  • 100% of the air is pulled into the facility exhaust system for appropriate treatment.
  • Type B2 cabinets must be hard-connected to an exhaust system.

Class III Total Containment Cabinets

Class III biological safety cabinets are gas-tight, designed for use with high risk biological agents. Class III cabinets provide the highest level of personnel, product and environmental protection. Because of the sensitive nature of most procedures performed within a Class III cabinet, Baker builds each BSC system to exact customer specifications.

Typical applications include:

  • Working with emerging diseases or diseases marked for near eradication.
  • Weighing and diluting chemical carcinogens.
  • Working with high concentrations of low to moderate risk agents.
  • Working with large amounts of low to moderate risk agents.
  • Use of equipment or instrumentation generating high aerosol volumes.
  • Maximum containment of highly infectious or hazardous experimental materials.
  • An extra level of safety not available in Class I or II cabinets.