Fume hood

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Fume hood

A fume hood (also known as a fume cupboard or fume closet) is a type of ventilation system primarily 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 of fume hoods are ducted and recirculating (ductless). The principle behind the operation of a fume hood is to contain, dilute, and remove hazardous substances emitted from chemicals, experiments, or processes.

Function and Design

The primary function of a fume hood is to exhaust hazardous gases, dust, mists, and vapors from a confined location to protect the user from inhaling them. The design of a fume hood involves a movable front sash or window that users can raise or lower to access the interior workspace. Air is drawn from the laboratory space into the fume hood and then either expelled outside the building (ducted) or filtered and recirculated back into the room (ductless).

Types of Fume Hoods

Ducted Fume Hoods

Ducted fume hoods are connected to the building's ventilation system and direct the contaminated air outside. They are suitable for handling highly hazardous materials since they completely remove the air from the work area.

Ductless Fume Hoods

Ductless fume hoods filter the air through activated carbon or HEPA filters before recirculating it back into the laboratory. They are more versatile and easier to install but may not be suitable for all types of chemicals or high-risk applications.

Safety and Usage

Proper use of fume hoods involves regular maintenance, including checking airflow and filter saturation. Users should always ensure that the sash is lowered to the recommended height during operation to maximize containment. It is also important to avoid rapid movements near the fume hood opening, as this can disrupt the airflow pattern and reduce its effectiveness.

Regulations and Standards

Fume hoods are subject to various regulations and standards to ensure their safe operation. In the United States, the American National Standards Institute (ANSI) and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) provide guidelines for the performance and testing of fume hoods. Additionally, the Occupational Safety and Health Administration (OSHA) sets exposure limits for hazardous substances that may be encountered in fume hood operations.

Environmental Impact

While fume hoods are essential for safety in laboratories, they are also significant energy consumers due to the large volumes of air that must be moved and conditioned. Efforts to reduce their environmental impact include the development of low-flow and high-efficiency fume hoods, as well as the implementation of laboratory practices that minimize the need for fume hood use.

See Also

• Laboratory safety
• Chemical hood
• Ventilation
• Occupational safety and health

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