ABC of Safety in the Biological Sciences
A fume or chemical hood is used to prevent flammable or toxic vapours entering the laboratory environment. Generally fume hoods are constructed with a face velocity sufficient to keep contaminants within the confines of the hood and of a material capable of withstanding fire for several minutes. Their location within the laboratory should be as far away from foot traffic as possible to prevent cross current airflow and eddying near the face of the hood.85 86 The work surface of fume cupboards must be flat, sealed and capable of containing any spills whilst materials should be handled a minimum of 150 mm from the face of the hood.
Fume extraction needs to be used where xylene, chloroform or formaldehyde are used and particularly over coverslip mounting areas, tissue processors and in tissue dissection areas. Down draft ventilation built into benchwork, rather than conventional upright fume hoods are more effective extractors where heavy fume removal is required, such as with formalin and xylene.
Fume cupboards must not be used as storage areas for solvents or any other dangerous material or for any purpose other than that for which it is designed (infectious materials should be handled in bio-safety cabinets).87
An example of a Pathogen Handling Cabinet with recirculated air through carbon filters.
The exhaust gases from fume cupboards must be vented to the exterior of the laboratory unless drawn through specific filters before re-entering the laboratory atmosphere. The location of exterior vents must be well away from fresh air intake ducts. Shut off valves for gas, electricity, water and so on should be located outside the hood enclosure. Fume hoods must be checked regularly to ensure optimum performance.