A fume hood is an enclosed work space in a laboratory that prevents the outward flow of air. Fume hoods cab be designed for work with inorganic or radioactive materials, or with biological materials. Biological fume hoods can be equipped with filters, to ensure that the air entering and exiting the cabinet is sterile. This minimizes the risk of exposure of laboratory personnel to biological agents that could be a health threat. Also, the work surfaces and materials inside the fume hood are protected fromcontamination from airborne bacteria or viruses . The latter is of particular relevance in some viral research, where the tissue surfaces used to grow the virus are prone to contamination.
The design of fume hoods differs, depending on the intended purpose (general purpose, chemical, radioisotope, biological). But all fume hoods share the feature of an inward flow of air. In biological fume hoods the flow of sterile air is typically from the back of the cabinet toward the laboratory worker, and from the top of the fume hood downward across the opening at the front of the hood. This pattern of airflow ensures that any microorganisms residing on the laboratory worker are not carried into the work surface, and that no air from inside the cabinet escapes to the outside of the cabinet. Any air that is exhausted back into the laboratory first passes through filters that are designed to remove biological and viral contaminants. The most popular type of biological filter is the high-energy particulate air (or HEPA) filter.
Biological fume hoods can have a moveable, protective glass partition at the front. Most hoods also have a gas source inside, so that sterile work, such as the flaming of inoculation loops, can be done. The fume hood should be positioned in an area of the laboratory where there is less traffic back and forth, which lessens the turbulence of air outside the fume hood.
The filtering system of biological fume hoods restricts its use to biological work. Work involving noxious chemicals and vapors needs to be conducted in another, specially designed chemical fume hood.
The construction of fume hoods is conducted according to strict protocols of safety and performance monitoring. In normal laboratory use, the continued performance of a fume hood is regularly monitored and test results recorded. Often such checks are a mandatory requirement of the ongoing certification of an analysis laboratory. Accordingly, laboratories must properly maintain and use fume hoods to continue to meet operating rules and regulations.
See also Bioterrorism, protective measures; Containment and release prevention protocol