A fume hood is one of the few pieces of lab equipment that is tied into the building itself. It connects to the exhaust system, it affects how much conditioned air the room needs, and it usually stays in place for decades. Picking the wrong one is expensive to undo.
The good news is that most selections come down to a short list of questions about the work the hood will contain. This guide walks through those questions and the hood type each one points to.
Start with the work, not the model number
Before comparing hoods, write down the answers to these:
- What chemicals and processes go inside? General solvents and reagents, radioisotopes, and perchloric acid each call for a different interior.
- How big is the apparatus? Measure the tallest and widest setup you expect to run, including glassware above the work surface.
- How much exhaust can the building supply? Every hood removes conditioned air from the room. In a lab with many hoods, exhaust volume drives HVAC sizing and operating cost.
- Who uses it? A research chemist, a QC technician, and a class of first-year students need different things from the same enclosure.
General chemistry and biology: bench hoods
For routine chemical handling, a bench-mounted hood installed above a work surface or base cabinet is the standard answer. The F-100 Series bench fume hoods are general-purpose hoods for chemistry, biology, research, teaching, pharmaceutical, biotech, and industrial QC labs.
The F-100 Series comes with a white fiberglass reinforced polyglass liner as standard and is offered in multiple widths and depths, with plumbing, electrical, and service fixture packages. Select configurations are available in ADA-accessible layouts.
If nothing on your list above is unusual, this is where most projects land.
Apparatus that won't fit in a bench hood
Two situations push a project out of the standard bench hood: equipment that is too tall, and equipment that is too large to lift onto a work surface at all.
- Tall setups. The F-600 Series OS Height fume hoods have a 60" interior height, compared with the standard 48" bench hood interior, and come in 24" and 30" clear interior depths. They suit distillation setups, reflux systems, and vertical glassware.
- Large or floor-standing equipment. The F-200 Series walk-in fume hoods are floor-mounted, so equipment rolls in rather than being lifted. They are used for pilot-scale work, large apparatus, chromatography, and barrel storage. Depending on the model, they can be configured as a standard floor-mounted hood, a 30" deep hood, a double-depth hood, or a double-depth, double-sided hood.
When exhaust air is the constraint
A conventional fume hood is typically designed around a face velocity of 100 feet per minute (FPM). In a building with dozens of hoods, that adds up to a large volume of heated or cooled air leaving through the roof.
The F-300 Series Isolator³ high-performance fume hoods are designed to maintain containment with less exhaust. Depending on configuration and project requirements, they can operate as low as 60 FPM. They are available in bench-mounted and floor-mounted versions.
This is also the point to decide between two ways of controlling exhaust:
- CAV (constant air volume) exhausts the same amount of air whether the sash is open or closed. It is the standard operation across the F-Series.
- VAV (variable air volume) reduces exhaust as the sash closes. It is available as an option and needs to be coordinated with the building's HVAC controls.
Bring your mechanical engineer into this decision early. The hood and the exhaust system have to be designed together.
Chemistry that needs its own hood
Some work should never go in a general-purpose hood.
Radioisotope and biological work. The F-400 Series radioisotope fume hoods use stainless steel interiors with coved containment chamber corners, which reduce hard-to-clean seams. Their reinforced work surfaces help support lead shielding where the application requires it.
Perchloric acid. Perchloric acid leaves residues that have to be washed out of the hood rather than left to build up. The F-500 Series perchloric acid fume hoods include Type 316 stainless steel liners, baffles, and work surfaces, coved corners, an integral trench drain, and a washdown system. Ductwork, drainage, washdown flow, and blower selection all need to be coordinated with the hood, so review these applications at the start of a project.
Teaching labs
In a classroom, the instructor needs to see what every student is doing. The F-EXP II Explorer educational fume hoods have glass side panels and can be ordered with either a painted steel back or a tempered glass back. They work in wall or island layouts and are available in 48", 60", and 72" widths.
Choose a sash style
The sash is the movable glass panel at the front of the hood, and it is the part users touch every day. Most F-Series hoods offer four styles:
- Frameless vertical slides up and down and gives the clearest view.
- Framed vertical works the same way with a framed glass panel.
- Horizontal uses panels that slide side to side, so a user can work behind a panel.
- Combination has horizontal panels set in a vertical-rising frame, giving both kinds of access.
Think about how people load equipment into the hood and how they work at it once it is set up. The answer is often different for each.
Plan for the years after installation
The sash system is one of the most common failure points in a fume hood. Cables, chains, pulleys, and counterweights wear with daily use. LF Systems services hoods from virtually all manufacturers, with programs for sash rebuilds and scheduled preventive maintenance. See our fume hood repair and maintenance services for details.
Where to go from here
LF Systems is an authorized ICI Scientific dealer and has served labs in Delaware, Maryland, Pennsylvania, and New Jersey since 1983. If you are planning a new lab or replacing an existing hood, the fume hood catalog (PDF) lists every model and option, and you can contact us to talk through your application.