A. The face area for a
hood with a combination sash is based on the opening through the horizontal
siding panels. It has roughly one half the face area of the same size hood with
a vertical sash. Therefore, the hood with a combination sash requires a
smaller (restricted) bypass even if it is to be used for constant volume
operation. In fact, having an open bypass provides no operational benefits
and increases the exhaust requirement for the hood as air must be drawn
through the bypass into the hood. The only time an open bypass is required is
if the exhaust volume is based on the sash raised vertically rather the
opening through he horizontal panels.
fan switch requires the installation of a Square D Thermal unit to function.
The thermal unit is not supplied with the switch as it must be selected based
on the full load amperage of the fan motor.
* Fan switch on Kewaunee fume hoods is rated for 1 HP motors or less
indented portion of the work top defines the safe working area of the hood
where contaminants can be generated without exposing the hood user. This
safe working area starts 6" behind the sash opening. The hood user is
likely to be exposed to any contaminants generated in front of this safe
working area due to the eddies in front of the use's body.
A. They are located on the right vertical facia
behind the top front panel.See
A. Normally the hood
face velocity is measured with the sash fully open. However, if the hood has a
gravity sash stop (Option 8) or a sash label (F-4803-00) to indicate the safe
sash height, the face velocity should be measured with the sash at the stop or
A. No, the face velocity on an
open bypass hood will increase as the sash is closed. The bypass limits the
increase in face velocity to no more than three and a half times the velocity
with the sash closed. This allows the hood to maintain a constant exhaust
volume flow rate.
according to NFPA 45 Fire Protection for Laboratories Using Chemicals,
laboratories and hoods are unclassified electrically with respect to Article
500 of the National Electrical Code. Where there is an extraordinary hazard,
the user may wish to use explosion-proof electrical fixtures for added
A. The most widely used standard for
testing hoods is the ASHRAE 110 Method of Testing Performance of Laboratory
Fume Hoods. This standard has sections for visualization of flow patterns,
measuring face velocity, and measuring containment using a tracer gas. In
addition the SEFA 1.1 Laboratory Fume Hoods Recommended Practices has sections
on visualizatio n of flow patterns and measuring face velocity.
A. OSHA does not have specific requirements for
fume hood face velocity. The most widely accepted references on this subject
ANSI/AIHA Z9.5 American National Standard for Laboratory Ventilation and the
National Research Council's Prudent Practices in the Laboratory recommend face
velocities of 80 to 120 feet per minute (FPM).
A. Usually the hood is
connected to a single 120 volt, 20 amp circuit. 12 gage THHN solid strand
wires in flexible metallic conduit is generally acceptable. For a
typical wiring diagram for a hood: Click
A. Yes, in most instances it is preferable to have the alarm
deactivated when the hood exhaust fan is off. If the hood fan is off and the
alarm is powered, the air currents created by people walking past the hood may
cause the alarm to momentarily go to "NORM". When the air current subsides the
audible alarm will activate again. Many people find this
A. The fan should be remote from the hood, either
on the roof or a penthouse. In facilities with many hoods, several hoods may
be connected to a one exhaust fan.
A. The most often used material for exhaust ducting is stainless
steel. It has good chemical resistance and is noncombustible. For highly
corrosive applications PVC is often used. PVC is combustible and should be
used in such a manner that it does not compromise the fire protection of the
lab. For noncorrosive applications, galvanized steel may be
A. Kewaunee hoods that are wired at the factory and
contain only the following devices are listed under the UL 61010A-1 standard.
These devices are: 120 volt, 20 amp GFCI receptacles, 240 volt, 20 amp duplex
receptacles, light switches, fan switches and the Kewaunee Air Alert Alarm.
Hoods that contain other devices or hoods that are not wired at the factory
are not UL listed. All devices provided on Kewaunee hoods are UL listed.
In addition, fume hoods with Kemglass or Stainless Steel
liners are listed under the UL 1805 standard.
A. An acid storage cabinet vented through the hood work top will
have an exhaust flow rate of approximately five to ten cubic feet per
A. As a general rule, no. The
NFPA 30 Flammable and Combustible Liquids Code discourages the venting of
flammable storage cabinets. The purpose of the cabinet is to protect the
contents of the cabinet from a fire in the lab. It is difficult to vent a
cabinet without compromising its fire protection.
information consult one of the following publications or organizations.
"Prudent Practices in the Laboratory: Handling and Disposal of
Chemicals"ISBN 0-309-05229-7National Academy Press2101
Constitution Avenue, N.W.Washington, D.C. 20418PH:
ANSI/AIHA Z9.5 "Standards for Laboratory Ventilation"Stock # 143-EQ-93American Industrial Hygiene Association2700
Prosperity Avenue, Suite 250Fairfax, VA 22301PH:
703-849-8888aiha.orgASHRAE 110American Society for Heating Refrigerating and Air
Conditioning Engineers1791 Tullie Circle, N.E.Atlanta, GA
30329PH: 800-527-4723ashrae.orgNFPA 30, 45, and
70National Fire Protection Association11 Tracy DriveAvon,
MA 02322-9908PH: 800-344-3555nfpa.orgSEFA 1.1Scientific Equipment and Furniture Association7 Wildbird LaneHilton Head Island, SC 29926PH: 843-689-6878sefalabs.com