The device is an enclosure with a movable sash window on one side that traps and exhausts gases and particulates either out of the area (through a duct) or back into the room (through air filtration), and is most frequently used in laboratory settings.

The first fume hoods, constructed from wood and glass, were developed in the early 1900s as a measure to protect individuals from harmful gaseous reaction by-products.

They may be built to different sizes, with some demonstration models small enough to be moved between locations on an island and bigger "walk-in" designs that can enclose large equipment.

[1] A hearth constructed by Thomas Jefferson in 1822–1826 at the University of Virginia was equipped with a sand bath and special flues to vent toxic gases.

Soon after, in 1943 during World War II, John Weber, Jr. developed a fume hood concept with a dedicated exhaust fan, vertically rising sash window, and constant face velocity in response to concerns about exposure to toxic and radioactive substances.

The principle is the same for both types: air is drawn in from the front (open) side of the cabinet, and either expelled outside the building or made safe through filtration and fed back into the room.

[14] Specialty enclosures for teaching may allow for additional visibility by constructing the sides and back of the unit from tempered glass, intended so that several individuals can look into a fume hood at once, though they often have poorer ventilation capabilities.

[11] The frame and build materials used for a fume hood are selected based on anticipated chemical and environmental exposures over the life of the equipment.

In most cases, only the working surface at the bottom of the enclosed space is made from a liner material, which is most frequently built from epoxy resin or stainless steel,[23] but a fume hood may be lined with any of the following materials:[11] Most fume hoods are fitted with a mains-powered control panel and/or air flow-monitoring device.

Typically, they will allow for the manual or automatic adjustment of internal baffles, but are required by ANSI[25][26] and EN[21]: 233 [27] standards to provide visual and audible warnings in the following situations:[28]: 7 Some control panels additionally allow for switching mechanisms inside the hood from a central point, such as turning the exhaust fan or an internal light on or off.

In most designs, conditioned (i.e. heated or cooled) air is drawn from the lab space into the fume hood and then dispersed via ducts into the outside atmosphere.

[37] A major drawback of conventional CAV hoods is that when the sash is closed, velocities can increase to the point where they disturb instrumentation, cool hot plates, slow reactions, and/or create turbulence that can force contaminants into the room.

[37][39] The design of these hoods is intended to allow the unit to meet ASHRAE standards while maintaining a lower face velocity and thus consuming less energy.

[5] VAV hoods can provide considerable energy savings by reducing the total volume of conditioned air exhausted from the laboratory.

They have only a canopy, no enclosure, and no sash, and are designed for venting non-toxic materials such as smoke, steam, heat, and odors that are naturally carried upward through convection.

[33]: 145  They are employed in some situations to provide exhaust for large equipment that would be inconvenient to store or manipulate inside a fume hood enclosure,[42] or generally in a lab bench area where processes that require additional ventilation are performed.

[38]: 26 The production of recirculating fume hoods was only made possible after the invention of the HEPA filter in the 1940s,[3] and while the units were initially considered inadequate at providing worker protection from vapors, their design and performance have been improved from the 1980s onward.

Additionally, while typically not classified as such, the manner in which biosafety cabinets are operated when not connected to a duct system is functionally the same as a ductless fume hood,[47]: 417  though the applications of biosafety cabinets, combined with the relative difficulty in connecting them to a building exhaust system compared to a fume hood, result in different safety considerations.

Downflow fume hoods are encountered more frequently in applications involving powders,[54] and are comparable to laminar flow cabinets.

[55] Fume hood units designed for procedures involving perchloric acid feature a water-wash system in the ductwork and are often built from marine grade stainless steel or rigid polyvinyl chloride,[43]: 36  Because dense perchloric acid fumes settle and form highly reactive perchlorate crystals, the internal baffles of the fume cupboard and ductwork must be cleaned internally with a series of sprayers,[56] and all corners may be altered to be coved or rounded to further reduce the potential for buildup of crystals.

[21]: 230  The scrubber system is stocked with acid or base neutralizing salts to effectively remove the targeted chemical used in any planned procedures; this factor requires a higher level of maintenance than standard fume hoods,[43]: 47  and also produces hazardous wastewater.

For example, Harvard University's Chemistry & Chemical Biology Department ran a "Shut the Sash" campaign, which resulted in a sustained ~30% reduction in fume hood exhaust rates.

This translated into cost savings of approximately $180,000 per year, and a reduction in annual greenhouse gas emissions equivalent to 300 metric tons of carbon dioxide.

[80] The process of shutting off, or "hibernating", these fume hoods turned out to be difficult to implement unilaterally across equipment of different models and ages, and only produced significant cost savings when applied over a period of more than 3 months.

[5]: 9.H.3  Coupled with other space occupancy sensor systems,[84] these technologies can adjust ventilation and lighting use to effectively minimize wasted energy in laboratories.

[89]: 67  Depending on design choices and HVAC capabilities, the blower may be installed within or above the hood, or it may be positioned at the exhaust point, usually the roof of the building.

[23] One EN standard requires that the face of a fume hood be installed such that it is at least 1 metre (3.3 ft) from any space where there is frequent movement.

[88] These design standards may advise for considerations previously reserved for specialty hoods that improve aerodynamics and ease of cleaning, such as coved corners, beveled openings, and integrated acid-resistant sinks.