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Frequently Asked Questions

Biological safety cabinet vs. laminar flow hood?

The biological safety cabinet (BSC) is designed to provide protection for the operator, environment and product/process simultaneously whereas the laminar flow hood provides only product and process protection on the work surface.

 

Biological safety cabinets must be used when, in addition to the product, protection of the user and the environment are required. There are several options of class and varying levels of protection available in BSCs.

• Class I Biological safety cabinets are designed solely for operator protection.
• Class II and Class III protect the product or specimen, the user and the environment from contamination.
• Class II cabinets have open access to the work zone while Class III BSCs, often referred to as glove boxes, provides a barrier between the user and the work area.
• A class III biosafety cabinet is crucial for working with any biosafety level 4 agents or other dangerous materials, such as aerosols of pathogens or toxins.

The biological safety cabinet creates unidirectional laminar flow across the work surface following parallel patterns, maintaining a negative pressure inside the cabinet during operation to prevent contaminants from escaping the work area.

 

Laminar flow hoods are not biological safety cabinets. Laminar flow cabinets are designed to protect the product and process on the work surface only. They do not protect the operator or the environment, as the airflow pushes aerosols or particulates from the work surface toward the operator and the laboratory. Laminar flow hoods may be chosen to provide either horizontal or vertical airflow, depending upon application needs, as each configuration is best suited to specific applications.

 

For more information, see Vertical Laminar Flow Hoods vs. Biological Safety Cabinets.

Dead air box vs laminar flow?

The polymerase chain reaction (PCR) process utilized in genetic laboratories for DNA and RNA amplification is extremely sensitive to contamination, thus requiring a workstation to prevent contamination between samples. The PCR workstation is employed to provide the contamination-free environment necessary to prevent background and cross background of DNA and RNA. Air quality is sustained to guarantee particulates that could impact conclusions are not present, while intense UV lighting emitted between uses assures easy sterilization. Two types of PCR workstations or PCR hoods that aid the laboratory researcher are the dead air box and the laminar flow hood.

 

The dead air box provides a circulation-free environment for the amplification and manipulation of DNA and RNA, incorporating a timed UV light that permits sterilization between amplifications. A safety interlock switch prevents exposure to UV light when the sash is raised.

 

The laminar flow hood circulates and filters air smoothly and constantly in parallel layers, combining a clean air environment using HEPA filtration with timed UV light sterilization for optimal protection from sample contamination. Raising the bi-fold sash turns off the UV light and enables the blower.

 

For more information, see PCR Workstation: Dead Air vs. Laminar Flow.

Which is better - Horizontal or Vertical Laminar Flow?

The selection of a horizontal or vertical laminar flow hood is dependent upon the application as well as user preference, as both are effective methods of particulate protection. Whether horizontal or vertical, laminar flow hoods provide constant, unidirectional airflow that protects products on the work surface against particles and particulates. Both types are designed to prevent stagnant air or dead zones that cause particle buildup as well as turbulent, violent, or erratic airflow that creates swirls or unpredictable particulate movement resulting in contamination.

 

Horizontal laminar flow hoods present airflow in a horizontal direction the air moving forward from a filter positioned from the rear straight along the work surface. Choose a horizontal laminar flow hood if:

• You are using primarily small utensils and equipment that will not cause airflow disturbance; larger equipment within the path of horizontal airflow may cause greater turbulence.
• You are working with non-hazardous materials, as the air exits into the environment.
• Your application requires less turbulence on the work surface since the airflow does not hit any obstruction until exiting.
• You need the greatest control over contamination, as operator hands are positioned downstream of the sample.

Horizontal Laminar Flow
PROS	CONS
Greater product protection	Larger samples and equipment obstruct air flow
Reduced turbulence	Rear access required for filter change, servicing
No sash; easier to position equipment	Additional depth for rear mounted operator
Hands positioned downstream of sample	Fumes may blow in face of operator

 

Vertical laminar flow hoods provide a downward vertical flow from a filter positioned above the work surface. Air exiting the filter media passes unidirectionally from the unit ceiling and then across the work surface, sweeping particles out of the enclosure as it goes. Choose a vertical laminar flow hood if:

• Your application utilizes large equipment on the work surface, as vertical flow creates less turbulence when encountering large items within the airflow.
• Your application requires that soldering fumes or fine powders be used, as greater operator protection is provided.
• You need a taller, larger work space, as filters are generally positioned on top, providing greater height for the work surface.

Vertical Laminar Flow
PROS	CONS
Greater operator protection; sash provided	Airflow is obstructed if items are stacked
Less floor space needed for cabinet depth	Filter change, servicing may require step ladder
Top mounted filter ensures easy access	Tubulence created from air striking work surface
Less turbulence using large objects, equipment	Work surface depth is limited

 

For more information, see Which is Better - Horizontal or Vertical Laminar Flow Clean Benches?

What are the differences between the Basic Ductless Fume Hood and the RX Ductless Fume Hood Series?

Purair® Basic and Purair RX are both stand-alone units designed to provide reliable protection for the operator and the laboratory environment, incorporating Air Science engineering, a high efficiency ebm-papst EC blower and the innovative Multiplex™ Filtration System. Additional safety against particulates may be obtained utilizing an optional HEPA or ULPA filter. Both the Basic and RX models are available in three widths for standard or shallow depth cabinets.

 

The Basic Ductless Fume Hood is a compact unit ideal for laboratory with space limitations or when small quantities of harmful substances are handled. Offering high level performance at an affordable price, applications cover a wide range, from balance enclosures and compounding to robotics and pharmaceutical laboratories. Options and accessories offer additional customization.

 

The RX Class I Balance Enclosure meets USP 800 and USP 795 requirements for non-sterile compounding processes and delivers protection for the user and the environment from hazardous powders and particulates generated on the work surface. Applications include balance enclosures and compounding as well as powder mixing and weighing. A rear internal baffle provides a smooth horizontal airflow pattern, delivering less fluctuation in balance readings than with vertical airflow, resulting in more accurate measurements. Utilizing the exhaust port on top of the unit, the RX may be incorporated into a ducted laboratory system. Available options and accessories, including a microprocessor controller enable unique customization for specific laboratory requirements.

What are the differences between the Basic Ductless Fume Hood and Advanced Ductless Fume Hood Series?

Both the Purair®Basic and Purair Advanced Ductless Fume Hoods provide superior protection for the operator and the laboratory environment, incorporating Air Science® engineering, a high efficiency ebm-papst EC blower and the innovative Multiplex™ Filtration System. Additional safety against particulates may be obtained utilizing an optional HEPA or ULPA filter.

 

The Basic Ductless Fume Hood is a compact unit ideal for a laboratory with space limitations or when small quantities of harmful substances are handled. Offering high level performance at an affordable price, this model is available in three widths for standard or shallow depth cabinets, and is customizable with additional options and accessories.

 

The Advanced Ductless Fume Hood offers premium features suited for demanding, high performance applications, particularly in highly combustible environments. An air sampling port permits manual filter monitoring, while the integrated filter track and wheel systems ensures filter security and integrity. Optional Air Science Enhanced Filtration Technology developed for used with a wide range of core chemical families increases operator protection against fume and particle hazards. A broad selection of options and accessories, including a microprocessor controller, provide customization for specific laboratory needs. This model is available in seven widths for standard depth cabinets only.