Views: 0 Author: Site Editor Publish Time: 2023-02-02 Origin: Site
A fume hood (sometimes called a fume hood or fume hood) is a local ventilation device designed to limit exposure to noxious or toxic fumes, vapors, or dusts.
A fume hood is typically a large piece of equipment that encloses a work area on five sides, with its base usually at standing working height.Two main types exist, ducted and recirculated (no duct).The principle is the same for both types: air is sucked in from the front (open) side of the cabinet and either exits the building or is filtered to safety and returned to the room,this is for:
Prevent users from inhaling toxic gases (fume hoods, biosafety cabinets, glove boxes).
Protection of products or experiments (biosafety cabinets, glove boxes).
Protection of the environment (recirculating fume hoods, some biosafety cabinets, and any other type of fume hood if appropriate filters are installed in the exhaust stream).
Secondary functions of these devices may include explosion protection,spill control, and other functions required to get the job done within the device.Fume hoods are typically set against a wall and often have padding above to conceal the exhaust ductwork.Because of their recessed shape, they are often difficult to illuminate with normal interior lighting, so many interior lights come with a moisture shield.In front is a sliding window, usually glass, that moves up and down on a counterbalance.In educational versions, the sides and sometimes the back of the unit are also glass, so multiple students can see into the fume hood at the same time.Low airflow alarm control panels are common.Fume hoods are typically available in 5 different widths;1000mm, 1200mm, 1500mm, 1800mm and 2000mm with depths varying between 700mm and 900mm and heights between 1900mm and 2700mm Variety.These designs can accommodate one to three operators.For particularly hazardous materials,an enclosed glove box is available, which completely isolates the operator from all direct physical contact with the work material and tools.The enclosure can also maintain negative air pressure to ensure nothing can escape through tiny leaks.
Phenolic resins (general applications).
Fiber Reinforced Plastic (FRP).
Polypropylene (best material for most applications).
Square corner stainless steel (durability and heat resistance).
Rounded stainless steel (easier to decontaminate, suitable for radiochemical and biohazard applications).
Cement board (rough use).
Most fume hoods are equipped with a mains powered control panel.Typically, they perform one or more of the following functions:
Low airflow warning.
Warns that the opening in the front of the unit is too large ("high sash" alerts are due to sliding glass at the front of the unit being raised above a safe level, causing the wind speed to drop).
Allows exhaust fans to be turned on or off.
Allows interior lights to be turned on or off.
Specific extra functions can be added, for example, a switch to turn the washing system on or off.
Because fume hoods are constantly removing large volumes of conditioned (heated or cooled) air from the laboratory space, they consume a lot of energy.Energy costs for a typical range hood range from $4,600 per year in a mild climate like Los Angeles to $9,300 per year in an extremely cool climate like Singapore.Fume hoods are a major factor in making laboratories four to five times more energy intensive than typical commercial buildings.Most of the energy that fume hoods are responsible for is that required to heat and/or cool the air delivered to the laboratory space.Fans in HVAC systems and fans in fume hood exhaust systems consume additional electricity.Many universities run or have run programs to encourage lab users to reduce fume hood energy consumption by closing VAV sash windows as much as possible.For example, Harvard University's Department of Chemistry and Chemical Biology conducted a "close the sash" campaign that consistently reduced fume hood exhaust rates by approximately 30%.This represents an annual cost savings of approximately $180,000 and an annual reduction in greenhouse gas emissions equivalent to 300 metric tons of CO2.Other institutions reporting energy consumption reduction through fume hoods include MIT,North Carolina State University, University of British Columbia,University of California, Berkeley,University of California UC Davis,UC Irvine,UCLA,UC Riverside, UC San Diego,University of California, Santa Barbara University of Central Florida and University of Colorado Boulder.Newer people detection technology senses the presence of a hood operator in the area in front of the hood. A zone presence sensor signal allows ventilation valve control to switch between normal and standby modes.Combined with laboratory space occupancy sensors,these techniques can adjust ventilation according to dynamic performance goals.