A high performance fumehood is a laboratory ventilation device that is designed to limit exposure to hazardous or toxic fumes, vapors or dusts.
A fume hood is typically a large piece of equipment enclosing five sides of a work area, the bottom of which is most commonly located at a standing work height.
Two main types exist, ducted and recirculating (ductless). The principle is the same for both types: air is drawn in from the front sash opening side of the cabinet, and exhausted outside the building.
Other related types of laboratory exhaust devices include: clean benches, biosafety cabinets, glove boxes and snorkel exhausts. All these devices address the need to control airborne hazards or irritants that are typically generated or released within the local ventilation device.
All local ventilation devices are designed to address one or more of three primary goals:
Protect the user (fume hoods, biosafety cabinets, glove boxes);
Protect the product or experiment (biosafety cabinets, glove boxes);
Protect the environment (recirculating fume hoods, certain biosafety cabinets, and any other type when fitted with appropriate filters in the exhaust airstream).
"High performance fumehood" or "low-flow" bypass CAV hoods are the newest type of bypass CAV hoods and typically display improved containment, safety, and energy conservation features.
Low-flow/high performance CAV hoods generally have one or more of the following features: sash stops or horizontal-sliding sashes to limit the openings; sash position and airflow sensors that can control mechanical baffles; small fans to create an air-curtain barrier in the operator’s breathing zone; refined aerodynamic designs and variable dual-baffle systems to maintain laminar (undisturbed, non-turbulent) flow through the hood.
Although the initial cost of a high-performance hood is typically more than that of a conventional bypass hood, the improved containment and flow characteristics allow these hoods to operate at a face velocity as low as 60 fpm, which can translate into $2,000 per year or more in energy savings, depending on hood size and sash settings.
The less air exhausted from a laboratory the less air has to be supplied. Since supply air must be heated, cooled, filtered, dehumidified or humidified, this costs money. The less supply air the more the energy savings and hence lower operating costs.
Distinctly different approaches are applied in the development of these fume hoods in order to reduce exhaust airflow requirements.
These unique approaches have also resulted in improved awareness of the imperative requirement for fume hood user safety. For the purposes of this guideline, to be called "high performance" a fume hood must provide equivalent containment performance at a nominal sash face velocity of 60 fpm when at its normal operating position, as well as providing containment at full sash opening.
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