500 INDOOR AIR POLLUTION
recirculation throughout the entire building. Accidental recir-
culation is a serious hazard and should be guarded against.GLOSSARY OF TERMS RELATED TO FUME HOOD
SELECTIONBaffl e: An air director mounted off the hood’s inner
surface which causes air to move in specifi c patterns.
Blower: An air moving device utilizing a rotating
impeller within a housing to exhaust air.
BTU: (British Thermal Unit) The amount of heat required
to raise one pound of water one degree Fahrenheit.
Capture Velocity: Air velocity at the hood opening
necessary to overcome opposing air currents and cause
contaminants to fl ow into the hood.
CFM: (Cubic Feet per Minute) A volume of air moved
per minute.
Duct: A pipe system used to convey and constrain a
moving air stream.
Ejector: An air moving system which consists of a high
pressure air source passing through a Venturi nozzle, creating
a suction at the nozzle entry.
Face Velocity: The speed of air measured in feet per
minute across the fume hood sash opening perpendicular to
the sash.
HEPA Filter: A High Effi ciency Particulate Air Filter
rated 99.97% effective on particles 0.3 micron or larger.
Inches of Water: A unit of pressure equal to the pres-
sure exerted by a column of water one-inch high at standard
temperature.
Manometer: An instrument for measuring pressure. It is
essentially a U-tube fi lled with a liquid, normally water or
mercury.
Negative Pressure: Pressure within a system below that
of atmosphere, causing an inward fl ow of air.
Plenum: An air compartment maintained under pressure
which serves as a reservoir for a distribution duct.
Positive Pressure: Pressure within a system above that of
atmosphere, causing an outward fl ow of air.
Scrubber: A device used to wash effl uent air streams for
removing contaminants.
Static Pressure: The pressure exerted in all directions
when air moves through a duct system creating a resistance
to air fl ow. Measured in inches of water.
TLV: (Threshold Limit Value) The amount of air-borne
toxic materials that represents the maximum concentration to
which an average person may be exposed for 8-hours a day with
no adverse effects. (Usually expressed in parts per million.)
Transport Velocity: The minimum velocity required to
move particulates in the air stream.LABORATORY SAFETY GUIDELINESSafety rules should be followed at all times. A shortcut may
save you a few minutes, but cost you your life. Here are a
few guidelines that may make your laboratory safer.Hoods: Chemical hoods effectively remove toxic and
fl ammable vapors. Equipment in use should be completely
enclosed in a hood with adequate room allowed for experi-
mental procedures. When the apparatus is too large to be
housed in a hood and there is no possibility of toxic or fl am-
mable materials being released, anchored shields of safety
or wired glass should envelope the equipment. Hoods are
not designed to be used as storage areas. Remove unused
equipment and chemicals and store them in their proper
places.
Emergency Equipment and Procedures: Well-equipped
chemical laboratories have eye-wash fountains, deluge
safety showers, fi re blankets, fi re extinguishers, and emer-
gency exits. This equipment should be tested periodically.
In addition, being familiar with the locations and uses
of the equipment may save you needed time during an
emergency.
Personal Protection: Rubber aprons, asbestos gloves,
safety glasses, full face shields, and approved respirators
protect you from spills, burns, spattering chemicals, fl ying
fragments, and irritating fumes. In addition, the laminated
safety glass doors on chemical fume hoods protect you from
mishaps in the hood.
Health Monitoring: When biological agents or carcin-
ogens are used in the laboratory, special medical control
programs are necessary to monitor the workers’ health. If
radioactive materials or radiation-producing equipment such
as an X-ray diffraction unit are used, dosimeters or fi lm
badges should be worn to monitor exposures.
Labeling: Chemicals must be prominently and accurately
labelled. When a small quantity of material is removed from
a large container, immediately label the smaller container.
Containers for hazardous chemicals should have precautions
such as “poison” or “fl ammable”; indicated under the label.
After you have completed working with a particular mate-
rial, return the container to storage or dispose of the material.
Nothing should be left in open containers.
Equipment should be labeled U.L. or C.S.A. listed and
meet all federal and local electrical codes.
Eating, Drinking, and Smoking: Food, beverages, and
cigarettes, pipes, or cigars should not be permitted in the
chemical laboratory under any circumstances. Chemical
glassware should never be used to hold food. Always wash
your hands well before eating, drinking, or smoking.
Pipetting: Never pipette toxic, corrosive, or radioactive
chemicals by mouth; always use a rubber bulb or syringe.
Glassware: Cracked or chipped glassware should be dis-
carded to prevent cuts or scratches which can cause further
complications if chemicals contact the injury.
Always place a towel or cloth over glass tubing being
cut or broken. Fire polish sharp ends. When inserting a rod
or piece of glass tubing through a perforated stopper, wrap a
towel around your hand for protection.
Waste Disposal: Disposal of hazardous waste materials
requires special handling.
Place all broken glass in specially marked metal
containers—never in waste baskets or containers used for
paper or rags.C009_001_r03.indd 500C009_001_r03.indd 500 11/18/2005 10:29:58 AM11/18/2005 10:29:58 AM