A fume hood is the primary safety device in any laboratory that works with hazardous chemicals. It protects lab workers by containing and exhausting toxic fumes, vapors, and particles away from the breathing zone.
Choosing the wrong fume hood wastes money, energy, and space — or worse, fails to protect your people. This guide walks through the types of fume hoods available, the key specifications to evaluate, and how to match a fume hood to your specific lab needs.
How Fume Hoods Work
A fume hood is essentially a ventilated enclosure. Air flows into the hood through the open sash (the movable glass front panel), passes over the work area, and exits through an exhaust duct to the outside of the building. This continuous airflow creates a barrier between the lab worker and the chemicals inside the hood.
The key measurement is face velocity — the speed of air flowing into the hood at the sash opening, measured in feet per minute (fpm). Most safety standards recommend 80-120 fpm face velocity for chemical fume hoods.
Types of Fume Hoods
Bench-Top Fume Hoods (Ducted)
Bench-top fume hoods are the most common type. They sit on top of laboratory casework and connect to the building’s HVAC exhaust system through ductwork.
Best For
- General chemistry with acids, bases, solvents, and reagents
- Labs with existing duct infrastructure
- Procedures that generate moderate to heavy fumes
- Teaching and research labs
Key Specifications
- Widths: 4, 5, 6, and 8 feet are standard
- Sash types: vertical rising, horizontal sliding, or combination
- Liner materials: epoxy-coated steel (standard), polypropylene (acid), or stainless steel (perchloric acid)
- Airfoil sill for smooth air entry
Ductless Fume Hoods
Ductless fume hoods filter air through activated carbon, HEPA, or specialty filters and return it to the room. No ductwork connection is needed.
Best For
- Labs without duct access or in buildings where ductwork is impractical
- Teaching labs with low-volume chemical use
- Weighing applications and powder handling
- Supplemental hoods for occasional use
Important Limitations
- Only effective for the specific chemicals the filters are rated for
- Filters must be replaced regularly — ongoing cost
- Not suitable for high-volume chemical work or unknown chemical mixtures
- Some safety officers restrict their use for certain chemical classes
Floor-Mounted (Walk-In) Fume Hoods
Floor-mounted fume hoods extend to the floor, providing a large interior for tall apparatus, floor-standing equipment, or operations that require walk-in access.
Best For
- Distillation setups with tall columns
- Large reactor vessels
- Equipment on carts that roll in and out
- Pilot plant and scale-up operations
Distillation Fume Hoods
Distillation fume hoods are extra-deep bench-top hoods designed specifically for distillation apparatus. The added depth accommodates heating mantles, round-bottom flasks, condensers, and collection vessels.
Perchloric Acid Fume Hoods
Perchloric acid fume hoods are constructed entirely of stainless steel with integrated wash-down systems. Perchloric acid vapors form explosive perchlorates on organic materials, so standard epoxy or fiberglass hoods cannot be used.
Required Features
- All stainless steel interior and ductwork
- Built-in water wash-down spray system for interior and duct
- Dedicated exhaust system (not combined with other hoods)
- Routine wash-down schedule after each use
Exhaust Snorkels
Exhaust snorkels are flexible point-of-use exhaust arms that capture fumes at the source. They are not full fume hoods but provide spot ventilation for light fume sources.
Best For
- Soldering stations
- Light chemical dispensing
- Histology and pathology labs (formalin fumes)
- 3D printers and laser cutters
Key Specifications to Evaluate
| Specification | What It Means | What to Look For |
|---|---|---|
| Width | Interior working width | 4 ft (small), 5 ft (standard), 6 ft (large), 8 ft (multi-user) |
| Face velocity | Air speed at sash opening | 80-120 fpm (check your institution’s EH&S requirement) |
| Sash type | How the front panel opens | Vertical (most common), horizontal (energy saving), combo (most flexible) |
| Liner material | Interior surface material | Epoxy (general), polypropylene (acid), stainless (perchloric) |
| Exhaust volume | CFM required | Varies by width and face velocity — affects HVAC sizing |
| Utilities | Built-in services | Gas, air, vacuum, water, electrical outlets, cup sinks |
Sizing Your Fume Hood
How Many Hoods Do You Need?
- Count the number of people who work with chemicals simultaneously
- Each person performing fume-generating work needs their own hood or dedicated hood time
- Add hoods for dedicated processes that run continuously (digestions, reactions)
- Plan for 20-30% growth
What Width?
- 4-foot hoods — single-user, limited apparatus, weighing, sample prep
- 5-foot hoods — standard research work, most common size
- 6-foot hoods — multi-apparatus setups, teaching demonstrations
- 8-foot hoods — multiple simultaneous processes, shared teaching hoods
Energy Considerations
Fume hoods are the single largest energy consumer in most laboratories. A single 6-foot hood operating 24/7 can consume as much energy as 3.5 average homes. Ways to reduce energy use:
- Variable air volume (VAV) controls — reduce exhaust when the sash is lowered
- Sash management programs — train users to close sashes when not actively working
- Occupancy sensors — reduce airflow when no one is in front of the hood
- Ductless hoods for appropriate applications — eliminate conditioned air loss entirely
Installation Requirements
- Ductwork — dedicated or manifolded exhaust duct to the roof. PVC, polypropylene, or stainless steel depending on chemicals.
- Exhaust fan — sized for the hood’s CFM requirement. Located on the roof to keep ductwork under negative pressure.
- Supply air — the building HVAC must provide make-up air equal to what the hoods exhaust. This is often the largest infrastructure cost.
- Electrical — dedicated circuit for the hood blower, lights, and any internal outlets.
- Utilities — plumbing for gas, water, and drain connections.
Frequently Asked Questions
How much does a fume hood cost?
The hood itself ranges from $3,000 (small ductless) to $15,000+ (8-foot ducted). However, installation — including ductwork, exhaust fan, and make-up air modifications — can add $10,000 to $30,000+ per hood. The total installed cost of a ducted fume hood is typically $15,000 to $40,000.
Ducted or ductless — which should I choose?
Choose ducted if you work with a wide variety of chemicals, use chemicals at high volumes, or if your institution’s EH&S department requires it. Choose ductless only if you work with a limited, well-defined set of chemicals that the filters can handle, and your safety officer approves.
How often do fume hoods need to be tested?
OSHA and ANSI/AIHA Z9.5 recommend annual face velocity testing. Many institutions test semi-annually. The hood should also be tested after any maintenance, modification, or relocation.
What face velocity do I need?
Most institutions require 80-100 fpm at the sash opening. OSHA’s ventilation standard and ANSI/AIHA Z9.5 provide guidance, but your institution’s EH&S department sets the specific requirement. Higher face velocity is not always better — it can cause turbulence that reduces containment.
Can I put a fume hood anywhere in my lab?
Fume hoods should not be placed near doors, high-traffic walkways, HVAC diffusers, or operable windows. Air currents from these sources can disrupt the hood’s airflow pattern and reduce containment. The ideal location is along a wall away from cross-drafts.
Need help choosing fume hoods for your lab? Contact Labs USA for expert guidance on fume hood selection, sizing, and specification. We carry ducted, ductless, floor-mounted, distillation, perchloric acid, and specialty hoods for every application.
