A chemical fume hood can provide adequate protection for most laboratory processes
if they are used correctly. Fume hoods are analyzed and
reported on annually to assess performance
The following are some "practical" tips to optimize the protection
a fume hood can provide.
For a list of approved fume hoods click here.
- Is the fume hood functioning? The hood operator should determine
whether it is functioning before beginning any work. This can be done with an electronic
safety monitor or checking the airflow with a thin strip of paper. If the fume hood
is not functioning: stop and cover all reactions, then call Physical Plant, 206.685.1411,
- If necessary adjust the hood baffles properly before setting up any work.
Most fume hoods have adjustable rear baffles. This controls from where the largest
volume of air will be exhausted: the upper, middle, or lower air space. The total air
volume exhausted by the hood will not change when adjusting the baffles. Use of heavier
than air fumes are best exhausted with the lower baffles opened. Use of fumes lighter
than air or when high loads of heated fumes are generated, it is best to exhaust with the
upper baffles opened. Some fume hoods have baffles that are not adjustable; instead they
are fixed in the most optimal setting for general hood usage.
- Select proper exhaust speed setting. Some fume hoods have a two speed exhaust
fan with a local control at the hood. The LOW or SLOW exhaust setting is designed to
provide air exhaust for chemical storage within the hood. The HIGH or FAST exhaust setting
provides protection for working with chemicals (e.g. mixing, measuring, pouring,
distillations, etc.). Some local controls contain an "OFF" setting which should not be
used. The hood should be left running to provide adequate room ventilation along with
chemical fume ventilation.
- Work with the hood sash partially or completely closed. If this is
not possible, additional Personal Protective
Equipment (PPE) should be used to ensure adequate protection.
- Move work at least six inches inside the face of the fume hood.
This minimizes the effect of cross-drafts and eddies created by the hood
operator or by occupants walking by the hood. Also, keeping windows and
doors closed will control cross-drafts.
- Avoid overcrowding the fume hood work areas. Chemicals and
equipment not in use should be removed from the hood to a proper storage
cabinet. Large bulky equipment used in the hood will cause eddies that
can be reduced by making sure there is a 1-2 inch air space on all sides
including the bottom. Avoid using equipment that blocks the hood sash
from closing. A safer ventilation method may exist and should be pursued.
- Control reaction rates and observe process until completion. Controlling
the rate of vapor and particle formation can minimize the risk of exposure. Never
leave a reaction unobserved for an extended period of time, due to possible hood
failure or unexpected accidents/spills.
- Minimize fire hazard within the hood. Do not place electrical spark
producing equipment in a hood containing flammable chemicals. Never leave a
flame or heating apparatus unattended. No permanent electrical receptacles
are permitted inside the hood.
- Do not attach or insert exhaust ducts or snorkels to the hood without checking
with EH&S (206.543.9510) or Campus Operations (206.685.1411). Drilling holes into
the side of a hood increases the risk of fume exposure if not done properly.
The UW certifies fume hood performance and thus the hood should not be physically
altered without prior approval and consent.
For further information and questions, please call EH&S
Building and Fire Safety at 206.543.9510.