Fume Hoods

Before reviewing our fume hood operation procedures, it is important to know the following definitions.

Baffle
Removable plates incorporated into the rear or top of the work chamber to form a plenum between the work chamber and the exhaust duct connection to promote uniform scavenging of fume and the point of discharge.

Exhaust System
All exhaust air ductwork, fan and associated equipment installed between the point of connection to the fume hood and the point of discharge.

Face Velocity
The velocity of the air passing through the work opening of the fume hood measured in the plane of the sash. Measured in feet per minute (fpm), or litres per second.

Fume Hood
A fume hood is an enclosed work area that:

• Is designed to prevent the spread of fumes/vapours to operators and other personnel in the area.
• Is ventilated by an induced flow of air through a sash opening or working aperture the height of which maybe adjusted.
• Dilutes the fume/vapour
• By means of an exhaust system, provides for the safe and remote discharge of the fume/vapour outside the building.

HVAC System
Heating, ventilation and air conditioning system (H-vac) relates to air handling systems designed for air quality, temperature, humidity and odour control. It also provides make-up air.

Make-up Air
Air needed to replace the air exhausted from a room by the fume hood and other ventilation devices.

Plenum
A low-velocity chamber used to distribute static pressure (from the fan in the system) throughout its interior.

Sash
A transparent safety screen in the work opening of the fume hood, which can be positioned between the operator and the work chamber for protection. The opening can be adjusted vertically to vary the size of the opening and control the face velocity of air into the fume hood.

Sash Opening
The dimension of the opening in the direction of the sash movement.

Fume Hood Operating Procedures

• Conduct all experiments that generate air-borne contaminants inside a fume hood. Always wear chemical splash goggles and a labcoat when working in a lab.
• The fume hood should be inspected annually by E.H.&S. Check the green sticker. If the date is not within the last year, do not use the fume hood. Next to the date will be listed "fume hood performance summary". This should explicitly define the performance of the fume hood and operating parameters. The velocity of the fume hood should be greater than 80 fpm for the use with non-carcinogen chemicals. If carcinogens are being used, the face velocity must be greater than 150 fpm. Do NOT use carcinogens in a fume hood that has a red notice on it saying that it does not meet WSIB's minimum airflow requirements for use with carcinogens. Departments have indicated which fume hoods they need to meet the requirements to use carcinogens - these fume hoods do not have any notices on them.
• The fume hoods were tested at specific sash openings. To achieve the same face velocity seen during testing the stickers with arrows should be lined up. Raising the sash higher than the labelled height will reduce the fume hood's efficiency. If the opening is not suitable to your needs, telephone 978-3000 to have it retested at a different sash opening.
• Prior to the start of any lab that requires the use of a fume hood, a check should be made to ensure the fume hood is drawing air. Taping a Kimwipe to the inside of the sash can do this by checking to see that it is moving. If it is not or there does not seem to be sufficient flow, telephone 978-3000 to have the fume hood checked. E.H.&S. do not charge to test hoods. Be aware of changes in airflow as you are working.
• The face velocity normally ranges between 80 and 100 fpm. Air (and associated chemical fumes) can be pulled from the fume hood and into the breathing zone by a number of factors including: foot traffic, rapid arm/body movements, open doors and ventilation systems. Foot traffic in front of the fume hood should be avoided. Laboratory doors should be kept closed when the fume hood is operating.
• Chemicals and equipment should be at least 6-inches inside the fume hood. If work is done at the face of the fume hood, contaminants may be 300 times greater than if done at the 6-inch mark. A piece of tape at the 6-inch mark will help to keep the experiment inside the fume hood.
• Do not put your face inside the plane of the sash when air-borne contaminants are being produced. Always use splash goggles and wear a full face shield if there is risk of an explosion.
• If a fume hood is working when people are not present because the experiment is still ongoing, information must be posted on the sash showing the name of the person conducting the experiment, what the experiment is and what are the potential hazards of the experiment.
• Do not use the fume hood as an extra storage cabinet. Chemicals and apparatus obstruct the airflow of an experiment using the fume hood. If there is an incident in the fume hood, clean up will be more difficult. Keep all chemical containers sealed to prevent the build up of fumes.
• Large pieces of apparatus should be elevated to allow airflow with minimal turbulence, to flow under the apparatus to the baffle.
• No sources of ignition or spark must be present when flammable liquids or gases are being used. Permanent electrical plugs are not allowed in fume hoods.
• Keep the fume hood clean - remove old apparatus and chemicals. Clean any spilled chemicals following procedures established in your research group or as stated in the MSDS. Make sure the glass of the sash is clean, so you can see what you are doing. Waste disposal information can be obtained by telephoning Chemical Supplies & Services at 978-3570.
• The sash of the fume hood should be kept closed, except when working within the hood is necessary. Use sliding sash for partial protection during hazardous work. Do not remove the sash.
• Each fume hood in the Lash Miller Research Labs has its own exhaust fan and stack. Fume hoods on each of the four wings of the Davenport Research Labs are on a common exhaust fan header, each control independently operated exhaust suction valves.
• For further information regarding fume hood operation, see ANSI/AIHA standard Z9.5 - Laboratory Ventilation.