Overhead Fume hood
An overhead fume hood (also commonly called a canopy fume hood, ceiling-mounted fume hood, or hanging exhaust hood) is a type of ventilation device mounted above a workspace — typically suspended from the ceiling or attached to a wall/column — rather than being a traditional enclosed bench-top cabinet.
Key Features and Purpose
- It provides local exhaust ventilation from above, capturing rising fumes, vapors, smoke, heat, steam, odors, or light dust/particles at the source without enclosing the work area.
- Unlike standard ducted chemical fume hoods (the classic enclosed lab hoods with a sash), overhead versions leave the workspace completely open and unobstructed below, maximizing usable bench or table space.
- Air is pulled upward into a hood/canopy or capture arm/funnel, then exhausted through ducting (usually to the outside) or sometimes filtered in simpler models.
Common Types
- Canopy-style: A large, fixed hood (often rectangular or dome-shaped) mounted directly overhead. Ideal for large open areas or tasks producing rising contaminants.
- Hanging extraction arms / snorkel arms: Flexible, articulated arms with a hood or dome at the end that can be positioned precisely where needed. These often mount to the ceiling, wall, or workbench and are very common in modern labs.
- Simple hanging panels/visors: Lightweight PVC or plastic visors hung by chains for very basic capture of light fumes/solvents.
Typical Applications
- Laboratories handling non-highly hazardous or low-toxicity chemicals where full enclosure isn't required.
- Areas with heat/moisture/steam (e.g., autoclaves, dishwashing stations, or histology embedding).
- Welding, soldering, gluing, or metal finishing stations (to capture rising smoke/dust).
- Industrial or educational settings needing flexible, space-saving ventilation.
Advantages
- Saves bench space — nothing sits on the work surface.
- Excellent for rising contaminants (hot vapors naturally go up).
- Easier access and better workflow in some setups.
Limitations
- Less containment than enclosed fume hoods — relies on capture velocity and proper positioning; not suitable for highly toxic, volatile, or hazardous substances (e.g., where full enclosure and face velocity standards are mandatory).
- Effectiveness depends heavily on airflow design, distance from source, and cross-drafts in the room.
- Often used for light-duty or non-chemical fume extraction rather than heavy chemical work.
