CHEMICAL SAFETY
- Incompatible Chemical Hazard Groups (PDF)
- Chemical Storage Recommendations
- Fume Hoods: Frequently Asked Questions
- Fume Hoods: Important Parts
- Fume Hoods: Good Practices
- Fume Hoods: Specialty Lab Exhaust Ventilation
- Material Safety Data Sheets (link)
- Particularly Hazardous Chemicals
Recommended Chemical Storage Practices
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Separate chemicals by hazard class before arranging them alphabetically.
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Avoid storing chemicals on bench tops, fume hoods or on the floor. Keep them away from sunlight and hot conditions and follow manufacturer’s storage recommendations to ensure a stable product.
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Inspect storage containers periodically for damage, integrity or evidence of unwanted reactions. Clean spillage on the outside to prevent inadvertent contact by other lab occupants.
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Store chemicals below eye level on shelves with doors, lips or other restraints.
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Place the user’s name and the date received on all purchased materials.
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Keep volatile toxic and smelly chemicals tightly closed when storing them and use a fume hood when handling them.
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Use corrosion resistant storage trays or secondary containment to retain materials if the primary container breaks or leaks. These can be used to separate incompatibles if space is tight.
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Label cabinets that store hazardous materials with type of hazard.
For more information, see Chapter 5: Managing Hazardous Materials of the Chemical Hygiene Plan.
Fume Hoods and How to Use Them
Laboratory fume hoods serve to control exposure to toxic, offensive or flammable vapors, gases and aerosols. Fume hoods are the primary method of exposure control in the laboratory. At this campus, fume hoods do not have power switches and can’t be turned off by the user. All fume hoods must be in continuous operation and repairs are a priority.
A. Frequently-Asked Questions
1. How often is the hood checked?
Campus EHOS conducts hood surveys annually. The sticker should not be more than one year past the current date.
2. What is the sash position sticker?
This usually indicates the highest point the sash can be raised and still achieve a minimum 100 fpm flow rate – NOT the ideal working height. When using the hood, keep the sash at a height of 18 inches or less from the closed position.
3. Who will service my fume hood?
If you think there is a problem with the hood, notify your stockroom staff and take the fume hood out of service. COSE Health and Safety staff will check the hood and submit a work request to Facilities to have it repaired.
4. What does it mean when the air flow monitor goes off?
If air flow is outside an acceptable work range the hood monitor will trigger an alarm to notify the user. The monitor does not control air flow, it only measures air flow. The alarm mode could mean the air flow is too low, the hood is down (not working), or there may be a problem with the monitor. Stop using the hood and report the problem to the stockroom manager as soon as possible. When a hood alarms, lab workers should not attempt to stop or disable hood alarms.
5. How often are the air flow monitors checked?
COSE Health and Safety staff or a qualified contractor checks the monitors at least once per year.
6. What if my hood does not have an air flow monitor?
Fume hoods not equipped with a flow monitor must have a strip of Kim wipe or other tissue attached to the bottom of the sash to indicate that air is flowing. Inward movement of the strip indicates air is being drawn into the hood and users should check the strip before working in the hood.
7. What is the required air flow rate?
Face velocity is a measurement of the average velocity at which air is drawn through the face to the hood exhaust. The acceptable range of the average face velocity is 70-100 lineal feet per minute (lfpm) at any one point. The average face velocity must be at least 100 lfpm.
8. How are fume hoods different from biosafety cabinets and clean benches?
It is important to note that fume hoods, biosafety cabinets, and clean benches are not the same thing and serve different purposes.
- A fume hood is intended to protect the user from chemical hazards and does not offer product protection from unfiltered air. Potentially contaminated air is exhausted up through a duct to the room and is not recirculated.
- Clean benches are useful for dust-free assembly of sterile equipment or electronic devices. The air is usually discharged into the room under the sash, resulting in the air moving toward the user
- Biosafety cabinets provide inward airflow to protect personnel, downflow HEPA filtered air to the work area to protect the product and exhaust HEPA filtered air to protect the environment from particulate and aerosol hazards. Filtered air is then recirculated into the room.
B. Important Fume Hood Parts
1. Sash
Sash is the term used to describe the movable glass panel that covers the face area of a fume hood. Sashes can be vertical, horizontal, or a combination of the two. Many newer hoods are installed with a sash stop, which stops the sash at approximately a 18 inch work level.
2. Air foil (Sill)
The air foil or sill, located at the front of the hood beneath the sash, creates a smooth air flow, minimizing turbulence of the air entering the hood. The recessed work area is directly behind the sill. All work should be done at least six (6) inches into the recessed area.
3. Air flow indicators or monitors
Most of the newer fume hoods are equipped with air flow monitors. These monitors provide lab personnel with a constant reading of fume hood performance but do not affect the air flow in any way. Lab workers should not attempt to stop or disable hood alarms.
If air flow falls below an acceptable work range the hood sensors will trigger an alarm to notify lab personnel. The monitors can go into alarm modes for the following reasons:
- The sash has been raised to a height at which the hood can no longer exhaust a sufficient amount of air.
- The building air exhaust system is not working properly.
- There has been a power outage.
- Air flow is too high or there is too much turbulence (some models)
- The Monitor is faulty.
Hoods not equipped with a flow monitor must have a strip of Kim wipe or other tissue to indicate if air is flowing but cannot guarantee sufficient air velocity. Inward movement indicates air is being drawn into the hood.
4. Baffles
The baffles are movable panels located on the back wall of the hood that create slots in which air is exhausted. The pattern of the air moving into and through the hood is determined by the setting of the baffles. Only Facilities technicians are permitted to adjust the baffles. Once the baffles are set, they should not be re-adjusted by lab workers.
C. Good Chemical Fume Hood Practices
1. Using Equipment Inside Fume Hoods
- Place apparatus and equipment as far back as possible in hood for safety and optimal performance. Equipment should be placed a minimum of 6 inches inside the hood. Keep electrical connections outside of hood.
- Ensure that equipment or materials do not block the baffle vents in the back of the hood.
- When using a large apparatus inside the hood, place the equipment on blocks, when safe and practical, to allow air flow beneath it.
- Do not place electrical apparatus or other ignition sources inside the hood when flammable liquids or gases are present. Keep in mind that liquids with low flash points may ignite if they are near heat sources such as hot plates or steam lines.
2. Working with Fume Hoods
- When using the fume hood, keep your face outside the plane of the hood sash and remain alert to changes in air flow.
- Work at least 6 inches back from the face of the hood. A stripe on the bench surface is a good reminder.
- Wear eye protection as required in the specific lab when working with volatile, corrosive, or very toxic liquids.
- Avoid rapid arm and body movements in front of the hood including opening and closing the sash rapidly and limit traffic flow while using the hood. These actions may increase turbulence and reduce the effectiveness of fume hood containment.
3. Disposing of Waste
Do not use the hood as a waste disposal mechanism. Apparatus used in a hood should be fitted with condensers, traps, or scrubbers to contain and collect waste solvents, toxic vapors or dust.
4. Storing Chemicals
Always use good housekeeping techniques to maintain the hood at optimal performance levels. Excessive storage of materials or equipment can cause eddy currents or reverse flow resulting in contaminants escaping from the hood.
- Limit chemical storage in fume hoods. Keep the smallest amount of chemicals in the hood needed to conduct the procedure at hand;
- Store hazardous chemicals such as flammable liquids in an approved safety cabinet;
- Keep caps on chemical reagent bottles tight and check fitting on laboratory glassware to minimize vapor loss;
5. Positioning the Sash
- Do not remove sashes from sliding sash hoods. The 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 or panels except when necessary for apparatus set-up. Replace sash or panels before operating.
- Keep the slots of the hood baffles free of obstruction by apparatus or containers.
D. Specialty Lab Exhaust Ventilation
1. Walk-in hood
A walk-in hood is a hood which sits directly on the floor and is characterized by a very tall and deep chamber that can accommodate large pieces of equipment. If you have a walk-in hood, there may be special operating protocols, so check with COSE Health and Safety staff.
2. Fume exhaust connections: "snorkels"
Fume exhaust duct connections, commonly called snorkels, elephant trunks or flex ducts, are designed to be somewhat mobile allowing the user to place it over the area needing ventilation. However for optimal efficiency, these connections must be placed within six (6) inches of an experiment, process, or equipment. These funnel-shaped exhausts aid in the removal of contaminated or irritating air from the lab area to the outside.
3. Canopy hoods
Canopy hoods are horizontal enclosures having an open central duct suspended above a work bench or other area. Canopy hoods are most often used to exhaust areas that are too large to be enclosed within a fume hood. The major disadvantage with the canopy hood is that the contaminants are drawn directly past the user's breathing zone.
4. Glove boxes
Glove boxes are used when the toxicity, radioactivity level, or oxygen reactivity of the substances under study pose too great a hazard for use within a fume hood. The major advantage of the glove box is protection for the worker and the product. Check containment and condition of the gloves frequently.
5. Ductless fume hoods
Ductless fume hoods are more accurately described as "exhausted enclosures" and are suitable for some low hazard tasks but are not an acceptable substitute for truly toxic chemical work. Check with COSE Health and Safety staff if you are considering obtaining one of these enclosures.
Particularly Hazardous Chemicals
OSHA’s laboratory standard requires employers to make provisions for additional employee protection for work with particularly hazardous substances.
- Establishment of a designated area;
- Use of containment devices such as fume hoods or glove boxes;
- Procedures for safe removal of contaminated waste; and
- Decontamination procedures.
By definition, these chemicals include the following categories:
- select carcinogens
- reproductive toxins, and
- substances with a high degree of acute toxicity.
More information and partial lists of chemicals in these categories:
Chapter 5: Managing Hazardous Materials at C.O.S.E. of the Chemical Hygiene Plan
Appendix E: Particularly Hazardous Substances of the Chemical Hygiene Plan.
Also available are SOPs for the following chemicals:
Acetaldehyde (PDF)
Acrylamide (PDF)
Acrylonitrile (PDF)
Hydrofluoric acid (PDF)
Osmium tetroxide (PDF)
