Laboratory fume hoods and laminar flow hoods are types of specialized laboratory equipment designed to safely handle different types of hazards. Also referred to as clean benches, laminar flow benches, or biosafety cabinets, these containment devices often appear similar and all use directed airflow to provide a clean and sterile work environment. Despite these similarities, there are key differences in the level of protection provided and suitability for different laboratory tasks.
Laboratory fume hoods:
Are enclosed, ventilated workbenches that provide protection from harmful substances by directing air away from the worker and up into the hood. No filters are used and air is diluted as it travels through ductwork before being released outside the laboratory.
Chemical fume hoods provide protection to the worker and laboratory environment but do not provide a sterile workspace to protect samples from contamination. Fume hoods are suitable for tasks that involve hazardous drugs or chemicals, hazardous chemical fumes, volatile toxic vapors, odorous or reactive materials, toxic gases, aerosols, flammable materials, carcinogens, or hazardous chemicals that can easily spatter.
Laminar flow hoods:
Are primarily designed to protect lab samples and products from contamination by directing air through High Efficiency Particulate Air (HEPA) filters within an enclosed and sterile workspace. Different types of laminar flow hoods are available depending on the level of protection required for the worker and laboratory environment as well as the types of tasks being performed.
Horizontal laminar flow workbenches direct HEPA-filtered air horizontally, from back to front, across the worktable surface. Workers are positioned downstream from the airflow and can be potentially exposed to contaminants. Horizontal laminar flow hoods should not be used when working with infectious biological materials, pathogens, or highly toxic chemicals.
The horizontal airflow ensures a higher level of protection for lab samples from airborne particulates since the worker’s hands and gloves are positioned downstream from the air current. A horizontal flow also reduces turbulence on the work surface and is best suited to tasks that involve small utensils and equipment since larger objects can disrupt the airflow.
Vertical laminar flow workbenches direct HEPA-filtered air down towards the workbench and then out through holes in the surface or through an opening in the front of the enclosure. The downward airflow provides extra protection for the worker and laboratory environment and is commonly used for assembling parts, inspecting electronic devices, drug preparation, or preparing media.
Since the filter is located on the top of the hood, vertical laminar flow workbenches provide a taller workspace that is suitable for working with larger equipment. The vertical airflow also results in less turbulence from large objects.
Biological Safety Cabinets: also referred to as biosafety cabinets, go beyond laminar flow workbenches by offering additional protection for laboratory workers and the environment. Biosafety cabinets must be used when working with infectious microorganisms, pathogens, as well as other toxic materials and the cabinets are available in three basic classes depending on the level of protection required.
- Class I Biosafety Cabinets provide protection for laboratory workers and the lab environment but do not provide a sterile workspace. Class I Biosafety Cabinets work in a similar way as fume hoods by drawing air in and away from the worker, up into a HEPA filter, and then out into the environment.
- Class II Biosafety Cabinets provide protection for laboratory workers, products and samples, as well as the environment. HEPA-filtered air is drawn in from the front to provide operator protection and also flows downward onto the work surface to protect products from contamination. Air also passes through an additional HEPA filter before being released into the environment.
- Class III Biosafety Cabinets consist of air-tight enclosures with non-opening front windows and multiple HEPA filters that are designed to provide maximum protection for both the laboratory worker and environment. Class III biosafety cabinets are sometimes referred to as glove boxes since workers access the sealed internal space through attached arm-length rubber gloves. This type of cabinet is suitable for working with biosafety level 4 highly infectious agents and other dangerous materials.