Fume hoods are safety devices in environments where hazardous vapors, gases or particulates are present. Yet if not used correctly, these safety devices can quickly become unsafe.
Commonly found in research laboratories, educational science labs, chemical manufacturing facilities and industrial plants, these ventilation systems serve a vital role: protecting users from inhaling toxic substances and preventing the accumulation of flammable or reactive fumes.
By drawing contaminated air away from the user and expelling it safely, fume hoods reduce the risk of chemical exposure and help maintain a clean, compliant workspace.
Whether you’re a seasoned chemist or a high school science student, understanding how to properly operate a fume hood is critical to safety. Despite their protective design, fume hoods are not foolproof. Improper use or neglect can compromise their effectiveness, potentially endangering workers and violating health and safety regulations.
Here are the top 10 fume hood safety practices to help ensure your lab or facility remains a secure and compliant environment:
- Keep the Sash at the Proper Height
- Work at Least 6 Inches Inside the Hood
- Keep the Airflow Unobstructed
- Close the Sash When Not in Use
- Don’t Use Fume Hoods for Chemical Storage
- Regularly Inspect and Certify the Hood
- Use Proper Personal Protective Equipment (PPE)
- Avoid Rapid Movements in Front of the Hood
- Know the Limits of Your Fume Hood
- Label and Communicate
Keep the Sash at the Proper Height
The sash is the sliding glass window at the front of the fume hood. It should typically be kept at or below the marked
operating height, which is often around 18 inches. This height allows optimal airflow to sweep vapors away from your breathing zone and helps contain any unexpected splashes or reactions.
Operating with the sash fully open compromises containment and can disrupt the hood’s face velocity. This is the speed at which air is drawn into the hood. Keeping the sash low also acts as a physical barrier, offering added protection in the event of a fire or explosion.
Work at Least 6 Inches Inside the Hood
To ensure fumes are effectively captured, always perform work at least 6 inches inside the hood from the front edge. This is called the “safe zone” where airflow is most stable and effective at containing contaminants.
If you work too close to the front, eddies or turbulence can allow vapors to escape into the lab. Use the edge of the fume hood as a reference point, and consider placing a piece of tape or a marked line to help staff remember this boundary.
Keep the Airflow Unobstructed
Fume hoods rely on steady airflow to function properly. Blocking vents or cluttering the work surface with too many items
can impede air circulation. This reduces the hood’s ability to contain harmful substances.
Avoid storing chemicals or equipment in the hood permanently. Large objects should be elevated using stands or blocks to allow air to flow beneath them. This maintains laminar airflow and helps prevent dead zones where vapors can accumulate.
Close the Sash When Not in Use
Whenever you’re not actively working in the hood, close the sash completely. Not only does this conserve energy (especially in variable air volume (VAV) systems), but it also serves as a secondary containment measure in case of equipment failure or chemical release.
Many modern fume hoods have automatic sash closers or alarms to encourage this behavior. Even without automation, closing the sash should be second nature, much like putting a seatbelt on in a car.
Don’t Use Fume Hoods for Chemical Storage
Fume hoods are for temporary operations, not long-term chemical storage. Leaving containers in the hood increases
clutter and disrupts airflow. More importantly, it elevates the risk of spills, fire hazards or accidental reactions.
All chemicals should be stored in appropriate cabinets. Flammables should be stored in flammable storage, corrosives in corrosive cabinets, and so on. If certain items must stay in the hood temporarily, they should be clearly labeled and spaced to allow airflow.
Regularly Inspect and Certify the Hood
Fume hoods should be inspected at least once a year by qualified personnel to ensure they meet performance standards, particularly for face velocity and airflow patterns. Some labs require more frequent checks, especially in high-risk environments.
Look for a certification sticker on the hood that notes the date of the last inspection and the acceptable face velocity range, which is generally between 80 to 120 feet per minute (fpm). If you notice decreased suction or airflow noise changes, report it immediately.
Use Proper Personal Protective Equipment (PPE)
While fume hoods reduce exposure risk, they don’t eliminate it. Always wear appropriate PPE, including lab safety goggles, gloves and a lab coat. In some cases, face shields or respirators may be necessary depending on the chemicals in use.
The hood is a ventilation device, not a substitute for personal protection. Make sure your PPE matches the specific hazards associated with the materials you're handling. If you’re not sure, consult Safety Data Sheets (SDSs) for guidance.
Avoid Rapid Movements in Front of the Hood
Quick movements, whether from walking past or gesturing in front of an open sash, can disrupt airflow and draw contaminants out of the hood. These air disturbances, sometimes called “air turbulence,” reduce containment efficiency.
Be mindful when working around an open hood and encourage others not to linger or move quickly in front of it. Even something as simple as placing equipment gently on the counter instead of slamming it can help maintain stable airflow.
Know the Limits of Your Fume Hood
Not all fume hoods are suitable for all substances. For example, perchloric acid requires a specially designed hood with a wash-down system due to the risk of explosive salt formation. Radioactive materials or biological agents may require entirely different containment systems.
Before using a hood for a new procedure, confirm that it’s rated for the chemicals and processes involved. When in doubt, consult your Environmental Health & Safety (EH&S) department or lab manager.
Label and Communicate
Clear labeling of processes and materials in use improves fume hood lab safety for everyone. Temporary signs noting, for instance, “Do Not Disturb: Reaction in Progress” or “Caution: Toxic Vapors” help prevent accidents and confusion.
Effective communication among lab members, especially in shared spaces, is key. Always leave the hood clean and orderly for the next user, and report any malfunctions immediately so they can be addressed before someone else is exposed.
Looking for more tips? Check out this fume hood safety checklist to create a safer environment for your employees or students.
