TL;DR: Working in a fume hood keeps hazardous vapors out of your breathing zone, shields you from small splashes and flash fires, and contains minor spills. It only works when the sash is low, airflow is verified, and the hood is certified annually.
The importance of working in a fume hood comes down to one fact: it is the primary engineering control between you and hazardous chemicals, pulling a constant stream of air away from your breathing zone. When used properly, fume hoods can protect users and the environment from toxic gases, explosions, and spills.
Fume Hoods Provide Proper Ventilation
Chemical exposure in the lab happens most often through inhalation, because vapors pass through the lungs and into the bloodstream within seconds. Short-term exposure to hazardous chemical vapors can cause headaches, dizziness, and respiratory irritation. Repeated exposure to solvents like chloroform or carbon tetrachloride is linked to long-term liver and kidney damage.
A fume hood is built for the containment of airborne contaminants. It draws room air in through the sash opening, captures vapors at the source, and moves them away from the user.
Fume hoods can either be ducted or ductless:
• Ducted fume hoods connect to the building’s lab exhaust system, which carries contaminated air through ductwork and releases it above the roofline, where it disperses safely.
• Ductless fume hoods recirculate the air by filtering it before redistributing it back into the laboratory. They rely on activated carbon filters matched to the chemical family in use, such as organic solvents, acids, or formaldehyde. Filters saturate over time, so ductless hoods need a filter-life monitor and a fixed chemical inventory.
Can a Fume Hood Protect You from Fires and Explosions?
A standard fume hood is not blast-rated, but its sash adds a physical shield against splashes, small flash fires, and minor reactions. Most sashes use laminated safety glass, which cracks into a web pattern and stays in the frame instead of breaking into loose shards.
The sash should always be shut when the hood is not in use. If an explosion occurs when the sash is open, the glass and contents inside the hood will be spread around the laboratory, potentially harming other lab personnel.
How Do Fume Hoods Contain Chemical Spills?
A raised lip or dished work surface provides chemical spill containment and keeps minor liquid spills inside the hood instead of on the floor. These lips are several inches wide and act as catch basins for spills or breaks.
These “troughs” are the new standard for fume hoods, but most older hoods don’t come with this feature. However, additional spill containment products can be purchased for older hoods.
While fume hoods are crucial, they cannot protect against every laboratory hazard. Extremely hazardous tasks require specially designed equipment. Nevertheless, fume hoods remain indispensable in any laboratory setting.