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http://ppims.services.mcmaster.ca/pplant/index.html

Information Guide to Fume HoodsFacility Services

(ext. 24740)

By: Jassica Johnpillai and Kaylea CassanoJune 2013

• A fume hood is designed to protect researchers from inhaling hazardous airborne chemicals and materials that may be used in a lab

• Fume hoods contain and redirect chemical contaminants, and prevent their escape into the laboratory

What is a Fume Hood?What is a Fume Hood?

Two primary goals:• Protect the user from inhaling toxic fumes• Protect the product or experiment

Primary GoalsPrimary Goals

• Secondary functions of these devices may include explosion protection, spill containment, and other safety functions necessary to the work being done within the device

Secondary GoalsSecondary Goals

• There are three different designs of fume hoods– The first has its sash open vertically – The second has its sash open horizontally – The third opens both horizontally and vertically

Styles of Fume HoodsStyles of Fume Hoods

• The fume hood is designed to minimize the fluctuation in face velocity as a sash is lowered or raise

• Air enters the fume hood through the openings along the top and underneath the airfoil

How it Works How it Works

• Bypass Hood• Sash• Airfoil

Components of a Fume Hoods

Components of a Fume Hoods

• When the sash is in the fully closed position fumes can still be captured

• The baffle directs the air to follow specific flow patterns within the fume hood and also generates a uniform velocity of air

How it Works Continued How it Works Continued

Air is drawn in from the front (open) side of the cabinet, and either expelled outside the building or made safe through filtration and fed back into the room

How it Works Continued How it Works Continued

• Be aware of any differences in visual or audible cues that can be seen on the fume hood alarm

• Do not override these alarms• Keep the slots of the baffle free of obstruction• Never place your head inside the fume hood• Do not use the fume hood as a storage area for

equipment-this can cause airflow blockage and allow fumes to escape

• Substitute toxic chemicals with less hazardous materials whenever possible

Safety Safety

• First, turn on the light in the fume hood so that it is easier to see what is being done within the fume hood – Light switch usually located on the outside front face of the fume hood

When using a Fume Hood

• Secondly, check the fume hoods annual inspection sticker • Hoods are tested annually

When using a Fume Hood

When using a Fume Hood

• Thirdly, check the airflow digital monitor – Some fume hoods do not have a digital monitor

• If the fume hood is in alarm do not use the fume hood and call ext. 24740

When using a Fume Hood

• Finally, when finished turn off the light and close the sash fully to conserve energy

• Face Velocity is the speed at which air moves into the fume hood across the sash

• Face Velocity is at its safest when it is between 80 and 120 ft/min

• The Face Velocity of a fume hood is tested annually

What is Face Velocity?

1. Smoke Test 2. Face Velocity measurements3. Light and Sash operation 4. Valve operation5. Calibrating monitors6. Test emergency purge systems7. Examine the structure and the housekeeping of the fume

hood

How are Fume Hoods tested?

• Requires a smoke pencil to visually show the ability of the fume hood to remove airborne materials

• The Smoke Pencil is placed at different positions to show consistency of flow

Smoke Test

• Produces measurements of hood velocity in three or four readings depending on the size of the fume hood

• Readings taken with a calibrated micromanometer

• Results are shown on the hoods certification page on the Facility Services website

Face Velocity Test

• Fume hood testers check to make sure that all lights in the hood are working to maximize safety

• The sash is checked to be in working order– The sash does not stick when moved– The sash is not loose in its position

Light and Sash Inspection

Valve Operation

• Test the valve systems within labs• All valve types include an immediate response mechanical

assembly to maintain airflow when hoods are in use

Calibrate Monitors/Emergency

Purge

• Test fume hood monitor for calibration and calibrate when required • Test the Emergency Purge systems to ensure they are in working

condition

Structure and Housekeeping

• Finally, testers look at the fume hood itself to determine its working condition– This includes examining the various components of the fume hood

• For example: screws, lights, siding • Housekeeping of both the lab and the fume hood is important

– The lab is safer when there is less clutter– The fume hood itself has better airflow when it does not have large

objects within it

• Airflow can be disturbed which causes airborne contaminants to escape the hood– To minimize this occurring

stand as far back from the hood as possible

Safety

• It is important to conserve energy consumption and to lower our carbon footprint

• Each fume hood has stickers indicating proper sash height, they also have stickers to remind lab users to close the sash when not in use

Energy Efficiency

• One fume hood’s energy is equal to that of three to five households per year

• Average labs at McMaster contain four fume hoods per room… That is the equal to the energy consumption of twenty houses!

• Closing the sash is an amazingly simple act that has a huge potential to help the environment

Energy Efficiency

To learn more about McMaster’s fume hood policies please visit the Laboratory Safety Handbook:

http://www.mcmaster.ca/opr/html/mcmaster_home/main/search_results.html?q=lab+safety+handbook&cx=017110053273856412988%3Aakq6v26t6nm&hq=inurl%3Amcmaster.ca&cof=FORID%3A11

To reach Facility Services call 905-525-9140 (ext. 24740)

Or visit the website at:http://ppims.services.mcmaster.ca/pplant/index.html