Many medical and research laboratories require a completely sterile environment in which to carry out certain tasks. Cleanrooms provide this environment, designed so as to minimize the amount of dust and particles in the air. Laminar flow hoods are an important parts of any cleanroom. They provide a work space completely devoid of contaminants. These hoods provide protection through a constant flow of air. Different types are defined by the manner in which the air flows, and their level of air-tightness.

Horizontal Laminar Flow Hoods

Horizontal laminar flow hoods are so named for the way in which air flows through them. Air comes down from the top, but then turns and runs onto the sterile area in a horizontal direction. A large filter covers the wall facing the person working at the bench. They are intended to provide a sterile, particle-free work area. This type of hood floods the work area with a constant stream of positive pressure. Horizontal flow hoods primarily protect the substances being worked with, and not so much the lab worker.

Vertical Laminar Flow Hoods

Vertical laminar flow hoods keep the work area just as clean as horizontal laminar flow hoods but deliver the air in a different way. With vertical hoods, the air flows straight down onto the work area. The air filter with these flow hoods is therefore mounted directly above the work area. The air leaves the work area through holes in the base. Vertical flow hoods provide protection to both the substance being worked with and the person working.

Class I Laminar Flow Hoods

Class I laminar flow hoods are very simple laminar flow-hood styles. They provide adequate protection to both the user and the materials being worked with, but they do not protect the work substance from contamination. They are similar to chemical fume hoods, which contain hazardous fumes but do not disinfect.

Class II Laminar Flow Hoods

Class II laminar flow hoods provide an aseptic environment in addition to protection from fumes and gases. They protect competently from the dangers of hazardous materials, and are therefore ideal for that application.

Class III Laminar Flow Hoods

Class III laminar flow hoods cabinets provide the ultimate level of possible protection. They are gas-tight and so protect the worker from the danger of exposure to human pathogens. Therefore, any applications involving potentially infectious substances should use a class III hood.