Chemical Fume Hoods, Buying A Lab Fume Hood
A chemical fume hood (called also laboratory fume hood or fume cupboard) helps you being protected from exposing to hazardous contamination and cross contaminating harmful reagents.
Do you need the extra protection, when working with flammable and/or toxic chemicals? So, you need an OSHA compliant, ASHRAE 110 certified chemical fume hood!
Here is the guide to choose a right chemical fume hood:
Types of Chemical Fume Hoods:
The Conventional Fume Hood (CAV):
One of the most common laboratory fume hoods is chemical fume hood with the constant air volume (CAV). They are used for general protection of the laboratory workers.
Because the amount of air is constant in exhaust port, the face air velocity of a chemical hood is inversely proportional to the sash height. The lower the sash, the higher the face air velocity the hood provides.
CAV chemical fume hoods can be installed with or without a bypass feature.
- Simple non-bypass fume hood is the most economical design. The fume hood is an enclosed cabinet with an exhaust duct port and a movable sash on the front. Examples: Ducted Chemical Fume Hoods
- The bypass is usually available in the chemical fume hoods with sliding sash. The bypass perforations are located above the sash, prevents increase of face velocity as the sash reaches the fully closed position, as some air drawn through the top of the hood, keeping a constant volume of exhaust air regardless of sash position. Depends on the manufacturer design, the bypass could be blocked when the sash going up, nears to fully open position. (as in RAV Reduced air volume fume hoods) Reference: Fume Exhaust Hoods
Chemical Fume Hoods (VAV):
Laboratory fume hoods with variable air volume (VAV) feature more advanced air control system and designed to reduce energy. Compare to conventional hood with bypass, VAV hoods reduce the total quantity of supply and exhaust air, save heating and cooling energy costs. However, the VAV fume hood price is usually more than other types of lab hoods due to their complex design.
VAV chemical hoods incorporate a closed loop control system continuously monitors and adjusts the amount of air being exhausted to maintain the required face velocity. Based on the sash position, the air volume is controlled by either changing the damper position in the exhaust duct, or adjusting the blower speed.
Special Application Chemical Fume Hoods:
Canopy Fume Hoods:
Wall mounted, non-enclosure ducted canopy with no sash, installed above the equipment being ventilated. The canopy fume hood is not recommended for ventilating hazardous substances.
Basic Chemistry Fume Hoods:
General laboratory hood, light duty plastic enclosure, benchtop with ducting port. They usually come with optional work surface, base cabinet or stand and integral blower. not compatible for use with acids and corrosive. Best used for solvents and chemicals that will not corrode steel or react with plastics. See Available Bench-top Laboratory Hoods.
Medium Duty Chemical Fume Hoods:
Polypropylene or stainless steel ventilated enclosures, benchtop, optional work surface, stand, blower, duct port. Better choice for corrosive chemical vapor condensation. They can be used with a wide range of chemicals. For price check visit Polypropylene Fume Hoods, Stainless Steel Chemical Fume Hoods
Carbon-Filtered Chemical Hoods:
Ductless recirculating fume hoods, portable, with activated charcoal filter (Carbon filter). Filter absorbs most of chemicals and remove odors. These types of hoods generally have a fan & filter mounted on the top. Several different types of carbon filters available for use in a ductless fume hood, you need to choose one that’s’ compatible with chemicals you use under the hood. Visit Cleatech® Ductless chemical Hoods
HEPA Filtered Enclosures- Ductless:
Ductless exhaust hoods with HEPA filtration and integral fan, remove particulates from the air before recirculating and return to room. They can be used also with combination of filters. See ductless fume hood price
Powder Containment Hoods:
Ventilated containment enclosure HEPA filter, a fume hood for Pharmaceutical compounding and also allow pharmacists or pharmacy students to safely measure, or weigh prescription drugs. They can be used as a ductless or ducted exhaust hood. See USP <797> and <800> compliant Pharmaceutical compounding hoods
Downdraft / Downflow Fume Hoods:
Downflow fume hoods (downflow workstation), fumes and vapors are collected through perforations in the work surface in the bottom of workstation then filtered through HEPA or Carbon and return to room. It can be used as a benchtop or placed on a mobile cart. See more about downflow workstation and prices
Free-Standing Fume Hoods:
Freestanding chemical fume hood (ductless or ducted) is a workstation provides enough working space for large process equipment. Worktable can be placed under the hood without process being effected by the hood vibration.
Walk-in Fume Hoods:
Walk-in chemical hoods are large floor-mounted fume hoods with exhaust port used where laboratory equipment should be rolled into the hood or taller apparatus need to be placed under the hood. They allow the operator to walk in to set up equipment before using them.
Ventilated Storage Cabinets:
Flammable and corrosive storage cabinets with own dedicated exhaust. They’re used primarily for storage of flammable or corrosive materials.
Chemical Hood with Wash-down system:
These fume hoods have an internal water wash system that cleans the interior of the hood and ducting, to prevent a build-up of dangerous chemicals such as Perchloric acid.
Other Lab Safety and Containment Enclosures:
- Laminar Flow Hood/ Clean Bench with Exhaust
- Class I Biosafety Cabinet- Ducted HEPA Filtered Hoods
- Class II Biosafety Cabinets
- Class III Biosafety Cabinets- Containment Glove Box
Another consideration with chemical fume hoods is the material of construction and interior liner material that must be compatible with the chemicals they are exposed to. Epoxy coated steel hoods have high heat resistance and offer fair compatibility, but the steel can corrode quickly if the epoxy surface is damaged. Fiberglass and polypropylene are economical material have good heat resistance, offer high chemical resistance, and are a better choice when working with strong acids, solvents, or bases. Chemical fume hood with Flame Retardant Polymers are more expensive but meet the most rigorous FMRC 4910 testing standards for most aspects of flame retardation, self-extinguishing characteristics. Polyresins offer excellent chemical compatibility but poor heat resistance. Stainless steel chemical hood good resistance to a wide range of chemicals and excellent moisture and heat resistance but not compatible with some acids.