A chemical fume hood is critical in a lab. A well-designed hood, when properly installed and
maintained, offers a large degree of protection to the user, if it is used appropriately, and its
limitations are understood. A fume hood is a ventilated enclosure in which gas, vapors, and fumes are
contained. It is used to control chemical exposure to the user and lab occupants and helps to prevent
chemical release into the laboratory. A fume hood can also limit the effects of a spill by partially
enclosing the work area and drawing air into the enclosure through an exhaust fan.
An exhaust fan installed on top of the laboratory building pulls air and airborne contaminants through
ductwork out of the building.
In a well-designed, properly functioning fume hood, only about 0.0001% to 0.001% of the material
released within the hood escapes from the hood into the laboratory.
A hazard analysis can help determine if a fume hood is necessary for an experiment. Such an analysis
should include: a review of the physical characteristics, the quantity and toxicity of the materials to
be used, the experimental procedure, the volatility of the materials present during the experiment
and the probability of their release, the number or sophistication of manipulations, and the skill level
of the person performing the work.
Chemical fume hoods, when used properly, are one of the most reliable engineering controls in the
laboratory.
They Protect Workers by:
- Containing vapors, dust, gas, and fumes generated within the hood, and removing them as air flows into the hood and then out via the laboratory exhaust system;
- Contributing to laboratory ventilation as air flows through the hood; and
- Shielding the worker with a clear sliding window, called a “sash,” that contains aerosols and prevents injury from splashes, fires, or minor explosions that may occur inside the hood.
Before Using a Fume Hood:
- Ensure that you understand how the hood works;
- Ensure that you are trained to use the hood properly;
- Know the hazards of the chemical you are working with; refer to the chemical’s Safety Data Sheet (SDS) if you are unsure;
- Ensure the hood is operational and on;
- Ensure that the sash is open to the proper operating level, which is usually indicated by arrows on the frame; and
- Ensure that the air gauge indicates that the airflow is within the required range.
When Using a Fume Hood:
- Never allow your head to break the plane of the hood opening;
- For vertical rising sashes, keep the sash below your face and for horizontal sliding sashes, keep the sash positioned in front of you and work around the side of the sash;
- Use appropriate eye protection;
- Ensure that nothing blocks the airflow through the baffles or through the baffle exhaust slots;
- Elevate large equipment (e.g., a centrifuge) at least two inches off the base of the hood interior;
- Keep all materials inside the hood at least six inches from the sash opening. When not working in the hood, close the sash;
- Do not permanently store any chemicals inside the hood;
- Promptly report any hood that is not functioning properly to your supervisor. The sash should be closed, and the hood “tagged” and taken out of service until repairs can be completed; and
- When using extremely hazardous chemicals, understand your laboratory’s action plan in case an emergency, such as a power failure, occurs.
Remember:
Laboratory fume hoods are an important engineering control used to remove airborne contaminants from a worker’s breathing zone. Improper use or operation of a fume hood could result in exposure to hazardous chemicals, injuries, fires, and even explosions.
YOU ARE THE KEY TO LABORATORY SAFETY!!!
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