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Education and Resources > Library > Acumen
Terminology Changes in the 2002 Revision of NSF 49
NSF/ANSI Standard # 49 – 2002
Class II Biological Safety Cabinets Types
Introduction
For more than 20 years there has been confusion concerning Class II biological safety cabinet (BSC) terminology. This has led to problems in understanding just what the types of Class II BSCs are, and how they should be installed and used. The changes in the NSF/ANSI Standard 49 - 2002 are intended to resolve many of these issues. A good way to grasp all of this is to become familiar with the evolution of Class II BSC terminology. Achieving this should enable us to properly interpret the relevant literature which contains a myriad of terms that have been applied to Class II BSCs. Additionally, it will make it possible for us to understand each other when we discuss BSCs.
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Ergonomic Considerations In The Development of A Class II, Type A/B3 Biological Safety Cabinet
Introduction
The laboratory workplace is changing. More attention is being given to laboratory personnel, their work environment and ergonomics, the science of fitting the workplace to the worker. The Baker Company has developed the SterilGARD® III Advance° biological safety cabinet in response to these changes. This cabinet, used in laboratory investigation and protocols involving agents of low and moderate risk, includes a number of design features that improve worker productivity and comfort while being used during repetitive tasks.
A Baker Company design team was charged with researching ergonomics issues associated with biological safety cabinets and making recommendations as to a new cabinet design. The team considered cabinet shape, worker position, lighting, containment and a number of other issues in composing design criteria. What resulted is the industry’s first Class II, Type A/B3 biological safety cabinet that recognizes the principles of ergonomics and worker comfort and is built with Baker’s reputation for performance.
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Continuous-Flow Bypass For Improved Fume Hood Performance
Abstract
The "roll" of air which forms inside a fume hood immediately behind the sash can be a reservoir for contaminants. Air recirculates at that location rather than exiting the hood immediately. So contaminant concentrations may be higher in the "roll' than at other point inside the hood.
The matter is of some concern, because the roll is close to the breathing zone of the scientist performing the work. The current project investigated a means of reducing the concentration of contaminants directly behind the sash. If this concentration is reduced, any leakage would be less hazardous to workers in the lab.
The method, called the continuous-flow bypass, introduces a constant stream of air into the hood above the sash, delivering dilution air directly to the roll. The method reduced contaminant concentration by 50 to 90%, which significantly reduces the hazard potential of any leakage.
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Risks to Assess When Selecting Clean Benches And Biosafety Cabinets For Animal Research
Abstract
Many research animals require isolation. In the past, cage-transfer protective equipment was designed primarily to prevent contamination of such animals. While that concern has not diminished, recent events have focused attention on protecting lab workers as well. In some cases, contamination has spread from lab animals to attendants, and in many cases, occupationally-induced asthma has been linked to excessive exposure to animal residue. This paper surveys some of the literature describing passively-transmitted hazards which may be created when they are transferred, or when their cages are cleaned.
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Using A Constant Air Volume Controller To Insulate A Class II Biosafety Cabinet From Negative Effects of A Variable Air Volume Exhaust System
Abstract
Variable air volume (VAV) systems are often used to exhaust air from chemical fume hoods. VAV controls reduce the exhaust airflow in proportion to the actual need. Consequently the systems uses less fan power, and less energy is used to condition the replacement air.
Unlike fume hoods, however, biosafety cabinets require a constant flow of air to contain contamination and to protect products in the cabinet. When variable volume fume hoods are connected to the same exhaust system as a biosafety cabinet, the variation in total system exhaust flow can disturb the critical pressure relationships between air flows in the cabinet. Such pressure changes can allow contaminants to escape the cabinet, or allow lab contaminants to enter the cabinet. To avoid these problems, biosafety cabinets can be equipped with constant air volume (CAV) controllers. Such controllers sense flow changes in the cabinet exhaust system. To keep that flow constant, the controller opens or closes a damper located in the cabinet exhaust duct.
This research shows that CAV controllers can be effective in maintaining constant air flow. However, increases in room supply air can cause local flow turbulence which adversely affect cabinet containment. the test results show that keeping the cabinet airflow constant does not necessarily guarantee that the cabinet will perform properly.
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Using Thimbles To Connect Biological Safety Cabinets to Variable Air Volume (VAV) Exhaust Systems
Abstract
Variable-volume exhaust systems are a common feature of laboratory ventilation designs. By reducing exhaust airflow in proportion to the actual need, the system uses less energy to condition the make-up air. However, variable exhaust flows can disturb the critical pressure relationships between air flows in biological safety cabinets, which require a constant air flow to maintain performance. Changes in air pressures can allow contaminants to escape the cabinet, or allow lab contaminants to enter the cabinet.
To avoid these problems, BSC's are often loosely connected to a VAV exhaust system by means of a "thimble", which is in effect an exhaust hood mounted over the cabinet exhaust duct. This loose connection reduces the magnitude of the change in airflow inside the BSC as exhaust air flows fluctuate, so BSC performance is maintained. This paper describes three research projects which investigated the use of thimbles connecting VSC's to VAV exhaust systems. the research results can be useful to designers and end users of laboratory ventilation systems.
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Cycle Parameters For Decontaminating A Biological Safety Cabinet Using H2O2 Vapor
Abstract
Several studies have shown that hydrogen peroxide vapor (H2O2) can be useful in decontaminating HEPA filters, isolations chambers and centrifuge enclosures.1-3 However, before hydrogen peroxide can be used reliably in a biological safety cabinet (BSC), it is essential to establish the cycle parameters which allow full decontamination, and which minimize overall cycle time. This paper describes research which established the appropriate physical modifications and decontamination cycle parameters for the Baker Model SG-600, which is a Class II, Type A/B3 biological safety cabinet.
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Using Hydrogen Peroxide Vapor To Decontaminate Biological Safety Cabinets
Abstract
Recent research has shown that hydrogen peroxide vapor (H2O2) can be used to decontaminate biological safety cabinets (BSC's) as an alternative to formaldehyde or ethylene oxide. 1,2,3 H2O2 is non-carcinogenic, highly effective as a decontaminant and is environmentally benign. However, H2O2 vapor decomposes quickly, so the gas must be rapidly circulated throughout the BSC. Also, hydrogen peroxide vapor attacks some materials. Consequently, existing cabinets need physical changes and material substitutions so the potential advantages of H2O2 can be fully realized.
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