The primary purpose of local exhaust ventilation is to protect the employee from hazardous
airborne exposures. Local exhaust ventilation systems include exhaust fans, their associated
ductwork, and typically a work enclosure or material enclosure. Exhausted work stations
include, but are not limited to, fume hoods, laminar flow chemical hoods, and exhausted
biological safety cabinets. Gas cylinder cabinets and exhausted equipment enclosures are
examples of material enclosures.
In order for exhaust systems to function effectively they must be designed, installed,
maintained, and used according to recognized standards and good work practices. Any work
involving installation of local exhaust devices or any connection or modification to exhaust
ductwork must be handled through Facilities Planning and Design.
To provide for the protection of North Carolina State University employees from overexposure
to harmful airborne chemicals in accordance with recognized ventilation standards and University
This program covers the proper design, use, and maintenance of exhausted work stations including,
but not limited to, fume hoods, laminar flow chemical hoods, and biological safety cabinets that
are connected to exhaust ductwork.
- Assure that employees are trained in the correct use of the exhaust device.
- Maintain exhaust equipment according to manufacturer's or University guidelines.
- Adhere to University policies on obtaining, modifying, or repairing exhaust devices.
Environmental Health & Safety Center Responsibilities
- Audit the effectiveness of the Local Exhaust Ventilation Program for the University.
- Assist in selection, location and use of exhaust equipment.
- Assure effective programs exist for regular inspections of fume hoods, biological safety
cabinets, and laminar flow clean hoods.
- Assist in drafting design, performance, and inspection guidelines for exhaust devices.
Obtaining / Installing a Local Exhaust Device
- Contact Environmental Health and Safety (515-6862 or 515-6860) if the amount of ventilation
needed and/or the appropriate exhaust device for your purpose is not clear.
- Once the appropriate exhaust device and exhaust rates are known, submit a Facilities
Modification request. Your department approved Facilities Modification request will be forwarded
to Facilities Planning & Design who will determine if adequate exhaust is available, that the
proper equipment is selected, and provide a cost estimate for the project.
- If the addition of the exhaust device is approved, order the exhaust device from the selection
of models and suppliers approved by Facilities Planning & Design and EHSC. This list is
available from Purchasing. Note: Recirculating hoods are not to be used for work involving
- All new fume hoods, and new and existing laminar flow chemical hoods and biological safety
cabinets which are connected to exhaust ductwork, require an exhaust monitor and alarm.
Facilities Planning and Design maintains the current University specification for this equipment.
- The exhaust device, with appropriate real-time flow monitoring alarm, is installed by through
the Facilities Division. The Facilities Division will also balance the exhaust device and adjust
the alarm set points, as applicable. Other branches of the exhaust system are balanced as
appropriate. Exhaust taps into existing exhaust ducts may only be done through a request to Facilities Planning & Design. Modifying an existing exhaust duct or hood may reduce the effectiveness of the system in
capturing airborne contaminants.
- Exhausted work enclosures (e.g fume hoods, laminar flow chemical hoods, biological safety
cabinets) may not be used unless a certification sticker, indicating the exhaust flow is suitable
for equipment use, is present. Standard chemical fumehoods and laminar flow chemical hoods
cannot be used until a green sticker (containing the words Environmental Health and Safety Center)
has been affixed to the hood. The balancing sticker will show the recorded face velocity
as well as other relevant balancing information.
Using Local Exhaust Devices
- Exhaust devices should not be used for purposes for which their design is not intended,
for instance, using perchloric acid in a general purpose lab hood or using hazardous chemicals
in a recirculating hood. (Perchloric acid should only be used in a dedicated and approved hood.)
Also, laminar flow clean benches which blow HEPA filtered air toward an operator and contain no
means for contaminant capture and exhaust, are not to be used with hazardous materials. The
procurement of these benches is discouraged due to concerns about misuse. Contact EHSC for the
guidelines and for training on the use, function, and limitations of ventilation devices.
- Assure that high hazard processes have automatic shutdown controls should exhaust fail.
Normally closed pneumatic valves, flow limiting orifices, over pressure or over temperature
controls, and other appropriate safety devices may be needed for high hazard experiments and
processes. See Compressed Gas
Safety and Hazard Review
for additional information.
- Assure that exhaust devices used for chemical handling (
fume hoods, laminar flow chemical hoods, biological safety cabinets) are checked on an annual
basis for proper flow. Contact EHSC if certification sticker indicates date of inspection greater
than one year old. Assure exhaust monitors and alarms, where present, are always functional.
- Do not alter or tap into exhaust ducts or exhaust devices. Modifications to the exhaust system,
including adjusting dampers, penetrating walls or work surfaces, or adding or removing services
may only be performed through Facilities Planning & Design.
- Understand any ventilation alarms that are in place in your work area. Train all new employees
on proper work practices, meaning of exhaust alarms, and actions to take in the event of an
- Contact EHSC if there are changes observed in the exhaust device's performance, including a
change in face velocity or inadequate capture of contaminants. Notity your building maintenance
contact if you notice excessive noise or vibration.
- Contact EHSC for information on clean air hoods' maintenance, including HEPA filter changing,
decontamination and annual certification of biological safety cabinets. EHSC may be contacted for
a list of vendors who repair and certify laminar flow equipment.
Repair and Surplusing
Laboratory personnel are responsible for ensuring that equipment is safe for maintenance or
surplusing. All hazardous materials are to be removed from the hood and vicinity as appropriate.
All potentially contaminated surfaces are to be appropriately decontaminated prior to removal.
A radiation safety survey should be requested if needed (515-6857) . Before surplusing, and
after any necessary equipment cleaning/decontamination has been performed, radiation warning
signs should be removed.