Chemical Fume Hoods are one of the primary safety equipment devices in laboratories for handling hazardous chemicals. They are designed to capture, contain, and exhaust hazardous fumes generated inside their enclosure. When Fume Hoods are properly installed and maintained, they can provide a substantial degree of protection for the user.The face velocity measurement test is conducted annually to check the performance of fume hoods.The average face velocity with the sash opening of 45 cm shall be between 80-120 feet per minute ( FPM) (optimal 100 FPM or 0.5 m/sec).
All operations which are liable to produce hazardous or obnoxious concentrations of gas or vapours should be performed in a fume hood. This is to protect your own personal health and safety, as well as for the safety of others in the lab.
Fume hood users are expected to review the University of Windsor Fume Hood Manual which adresses fume hood safety operational and maintenance issues.
Benchtop Fume Hood
Picture from: “Prudent Practices in Laboratory: Handling and Disposal of Chemicals”, National Academy Press, 1995.
- The primary parts of the fume hoods are:
- Face: The face of the hood is the opening where air capture takes place
- Sliding Sash: Is the glass “window” that moves in the plane of the hood face that opens or closes the hood and protects the user during working.
- Air Baffle and Adjustable Slots: Direct the air flow within the hood
- Airfoil: Located at the bottom and sides of the sash help to reduce air turbulence at the face of the hood
- Duct: Connects the hood to the ventilation system and exhausts to the outside air.
General Safety Guidelines for Fume Hoods
- Keep the sash as low as possible, always making sure it is between you and your work.
- Never operate the hood unless there is some visual indication that the hood is operating. A tissue or Kimwipe ® taped to the sash can be used as an airflow indicator.
- Do not block airflow. Raise large objects 5 cm off the counter by placing them on blocks. This allows airflow underneath and prevents stagnant areas.
- Always set up apparatus as close to the back as possible. Work a minimum of 15 cm from the sash.
- Fume hoods used for experiments should not contain any unnecessary stored substances or apparatus. They can block air flow and create unnecessary hazards.
- Avoid placing your head inside the fume hood.
- The hood is not a substitute for personal protective equipment. Wear gloves, safety glasses, etc. as appropriate.
- All electrical devices should be connected outside the hood to avoid sparks which may ignite a flammable or explosive chemical.
- Close the sash completely when not working at the fume hood.
- Fume hood alarms should never be disengaged or turned off.
- Many fume hoods are equipped with a sash position alarm. When the sash is raised above 18 inches from the base, a buzzer will sound and a red light will begin flashing on the monitor alerting the hood user that the face velocity is below 80 feet per minute. To turn off the buzzer the sash has to be lowered below 18 inches.
- If hoses or cords must be inserted through the face of the hood, they must be run underneath the airfoil so the sash can close completely.
- Certain reactions and chemicals require specially constructed hoods. Examples are perchloric and hydrofluoric acid or high pressure reactions. Radioactive materials may only be used in hoods specially designed for radioactivity.
In Case of Spill or Fire Within the Hood
- Immediately close the sash completely if you can do so safely.
- Do not turn off the exhaust fan.
- Unplug all equipments within the hood (this assumes that the equipment is plugged into outlets outside the hood).
- Warn others in the lab and evacuate the area.
- Video: Proper Use of a Fume Hood (3:39 min.). EH&S UC Berkeley
- Video: Fume Hood Airflow & Operation (3:17 min). Labconco
Training and Certification Program
Overnight Experiment/Reaction Form
Complete the Overnight Experiment/Reaction Form (.pdf) for each potentially hazardous experiment or for functioning equipment left unattended in your laboratory fume hood.
Biological Safety Cabinets
It is essential to distinguish between fume hoods and biological safety cabinets. Biological safety cabinets are enclosures designed for containment of biological hazards.
They are equipped with special filters that remove potentially infectious agents such as microbes and spores. The filter does not remove vapors and gases, so Biological Safety Cabinets should not be used for chemicals.