Fume Hoods

What are Fume Hoods?

Fume hoods are the primary engineering control against inhalation exposure in chemistry and life-science laboratories. An enclosed cabinet with a movable sash, a work surface and a fan creates inward airflow so that vapours, fumes and airborne particles generated inside are drawn away from the operator and discharged. Ducted hoods exhaust to atmosphere through a building duct and fan, while ductless hoods filter and recirculate air into the room. Specialised designs handle specific hazards: acid digestion hoods resist corrosive vapours and may include scrubbers, and perchloric acid hoods add water washdown of the duct to prevent explosive salt deposits. Hoods protect operators rather than products, and are distinct from biosafety cabinets and laminar flow benches. Selection depends on the chemical list, the quantities handled, available building services and the applicable testing standard in the user's jurisdiction.

How do Fume Hoods work?

A fume hood maintains a controlled inward flow of air across the sash opening. The exhaust fan pulls air from the room through the opening, and a baffle system at the rear distributes it across slots at top, middle and bottom so no dead zones form. Face velocity, measured at the sash plane and typically 0.4–0.6 m/s, is the main indication of performance, though containment is also affected by sash position, cross-drafts and internal obstructions. Bypass and variable air volume (VAV) designs hold face velocity as the sash moves, with VAV modulating fan or damper output. A duct carries exhaust to the roof, where treatment such as carbon or scrubber media may be applied. Ductless hoods instead pass air through prefilter, carbon and sometimes HEPA stages before returning it to the room. Airflow monitors and alarms warn users when flow falls outside the safe range.

Where are Fume Hoods used?

Fume hoods are used wherever volatile, toxic, corrosive or odorous substances are handled. Organic and inorganic chemistry laboratories use them for solvent work, digestions and reactions. Pharmaceutical and biopharmaceutical laboratories use them for sample preparation, dissolution media and active ingredient handling, and quality control. Materials and electronics laboratories use them for etching, coating and cleaning. Teaching laboratories use them for undergraduate chemistry, and hospital and clinical laboratories for specimen digestion and staining. Specific hazards drive special designs: trace-metal analysis uses acid digestion hoods to control corrosive vapour and contamination, while perchloric acid digestions require dedicated washdown hoods. Universities, contract laboratories, environmental testing, mining assay and forensic laboratories all rely on hoods as a defined part of their exposure-control plan.

Which standards apply to Fume Hoods?

Fume hood performance and safety are covered by several regional standards. In Europe, EN 14175 parts 2 to 4 define safety and performance requirements, type tests and on-site tests. In North America, ASHRAE 110 describes tracer-gas containment and face velocity testing, and institutional guidance applies to installation and use. China uses GB/T 34269 and related GB codes. Ductless hoods are addressed by AFNOR NF X 15-211. General electrical safety follows IEC 61010-1, and laboratory ventilation design references local building codes. Materials, liners and service fittings should be selected to resist the specific chemicals in use. Where a supplier cites a certificate, treat it as a candidate until the exact model and test report are verified.

How do I select the right fume hoods equipment?

Select a fume hood by matching it to the chemicals and processes, then to the building. Build a chemical list with concentrations, quantities and operating hours; this determines whether a ducted or ductless hood is acceptable. Choose ducted hoods for unknown, high-volume or highly toxic substances and for heated perchloric acid. Pick the width, commonly 1200–1800 mm, to fit apparatus and operators, and confirm depth and internal height for tall setups. Specify the liner: epoxy or fibre-reinforced cement for general chemistry, polypropylene or stainless steel for acids. Decide between constant-volume, bypass and VAV airflow, considering exhaust capacity and energy cost. Add airflow monitoring, alarms, service fittings, sinks and base cabinets as needed. Finally, verify that make-up air, duct sizing and containment testing are planned with the building engineer before ordering.