Passing Label Signage
Restricted Label Signage
Hood closure signage
What is a Laboratory Hood?
What do the features do?
Fan and Stack-
Direct effluent upward at high velocity well above the roof.
Fan outside of building-
Ductwork inside building is under negative pressure to eliminate possibility of outward leakage.
Light-
Lights and electric outlets must be outside of hood or explosion proof to eliminate spark sources.
Baffles-
Provide uniform air flow through face. Put adjustable baffles in center position.
Sash-
Mechanical protection for user. Contains breakage and small explosions.
Bypass-
Maintain constant face velocity independent of sash position.
Airfoil-
Prevents dead space at front of hood, helps protect user from small spills.
What protection can you expect from proper use of a good lab hood?
Protection from airborne toxic materials.
Protection from small fires and "explosions"-if you keep the sash closed.
How do you get the protection?
Be sure air is moving into the hood. Some hoods have meters or alarms. Always use a tissue to verify that air is flowing into the hood.
Maintain air flow pathways front to back. Elevate large items so that air can flow under them. Align items from front to back instead of across the back of the hood.
Keep all work >15 cm behind sash opening
Keep heaters >30 cm behind sash opening
Close the sash as much as possible even when working in the hood. Hood ventilation is more effective with a smaller sash opening. Use a horizontal sliding sash or a blast shield when working with equipment that may break or splash.
Close the sash except when working in hood to protect people. In some cases, closing the sash also saves energy.
Have spill control materials and plans. Secondary containment, such as a low pan under equipment will help keep a small spill from becoming a large problem. A bucket of absorbent material such as bentonite clay ("Oil-dri") or vermiculite can be thrown on a spill to keep it from spreading. Spill kits can be purchased commercially or the Safety Department can provide a shopping list.
Understand and obey labels and placards, including sash height limitations.
Store chemicals and material elsewhere so that they do not become involved in a hood accident. The Safety Department can provide information on better storage alternatives, contact at 265-5000.
Keep adjustable baffles at the center position. Do not attempt to use another baffle position unless you have verified that it is better.
Use protective gear as needed (goggles, apron, shield, gloves)
Complement your other efforts with good personal hygiene. A fume hood cannot protect against skin absorption or accidental ingestion of chemicals.
What about special cases?
Perchloric acid-Use hot perchloric acid ONLY in a hood that is reserved for the purpose and equipped with a wash-down system. Perchloric acid vapors can condense in a conventional hood leaving explosive residues that can cause injury or fire.
Airborne radioactive materials-The Radiation Safety Program needs to review your work and the hood to assure safety.
Biological safety considerations-A certified Biological Safety Cabinet is preferred for work with biologically hazardous materials. Contact the Biological Safety Program at 3-2037 for additional information.
Are there alternatives to lab hoods?-YES!
Why?-Fume hoods are expensive. A typical laboratory hood costs $15-30,000 installed and uses about $2,500 per year in energy. In many situations, a less expensive alternative provides equal protection.
Ventilated storage cabinets for odorous chemicals can be installed for $1-2,000. Operating costs are about 0.3 percent of the cost of a fume hood.
Dedicated instrument exhausts use 10-50 percent of the energy of a fume hood, allow better access to the equipment and have much lower installed cost.
Benchtop exhausters can provide efficient ventilation to lab benches if mechanical protection is not needed. Teaching labs and production labs should consider this alternative.
"Ductless fume hoods"-NO! Ductless fume hoods are unsafe in research laboratories because of the varied and unpredictable nature of research work and the opportunities for accidental misuse.
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