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Chemical Fume Hood Policy

PURPOSE: To establish a protocol for the safe uses of chemical fume hoods (CFH). This includes performance testing, reporting and responding to equipment failure, scheduled maintenance, appropriate steps necessary to safeguard workers who perform repairs, and the responsibility for implementation of this policy.

SCOPE: This policy covers all university campuses, including Morningside, Medical Center, Lamont-Doherty Earth Observatory (LDEO) and Nevis

DEFINITIONS:
Face Velocity: Average linear air velocity into the exhaust system (i.e. fume hood) measured at the opening into the hood.
Capture Velocity: Air velocity at any point in front of the hood necessary to overcome opposing air currents and to capture the contaminated air into the exhaust hood.

PROCEDURES:
A. Laboratory Chemical Fume Hoods

Engineering controls are the first line of defense against workplace hazards, removing the hazard from the worker’s environment. This includes local exhaust ventilation (i.e., chemical fume hoods) to prevent exposure to gases, chemical vapors and aerosols. There are two basic categories of laboratory hoods: chemical fume hoods and biological safety cabinets. This policy outlines the design face velocity requirements and test procedures for chemical fume hoods. Biological safety cabinets are tested and certified by an independent contractor.

NOTE:The use of perchloric acid is prohibited in regular fume hoods.  It should be used only in the wash down chemical fume hood that has been designed for its specific use and manipulations. If you have any question consult EH&S.

1. Location
Fume hoods shall be located within a lab in such a way that their performance is not adversely affected by cross drafts. Cross currents, drafts and air currents from open windows, doorways, and personnel traffic flow directly influence hood containment ability

2. Fume Hood Performance Testing Procedure
a) Performance tests for hoods require:

i.   exhaust rate measured by a calibrated orifice;
ii.  linear air velocity measured in the plane of the fume hood face (face velocity); or
iii. heavy and light smoke tests at different fume hood sash positions.

The linear air velocity method is used to document performance of CFH by the Department of Environmental Health and Safety (EH&S). If additional problems are suspected with a particular hood, all three performance tests may be performed.

b) Face Velocity:
The measurement of hood face velocity is important for quantitatively determining the effectiveness of a chemical fume hood in capturing and removing materials emitted within it. The average face velocity (V, in ft/min or fpm) is the volumetric flow rate of the hood (Q, in ft3/minute or cfm) divided by the area of the hood face (A, in ft2). Adequate face velocity ranges from 80-120 linear fpm. Minimum face velocity is the minimum acceptable velocity at any point on the operating opening, for example 80 fpm. This should not be less than 95 percent of the as-designed average face velocity. Maximum face velocity is the maximum acceptable velocity at any point of the operating opening. Maximum face velocity should not be greater than 120 fpm to prevent creation of turbulent air currents within the fume hood.

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3. Fume Hood Testing Responsibilities and Procedures
EH&S shall perform chemical fume hood testing and certification annually. Average face velocity is determined by measuring velocity at evenly distributed points in the plane of the hood face in the following manner:

  • The sash is placed at the lowest working height, usually twelve inches. The plane of the hood face is divided into (at least) three equal in area sections. Face velocity is measured at the center of each section. The hood face velocity is the average velocity of these measurements.
  • The tester will place a certification sticker on the front of the hood, recording the test date, face velocity at a 12” sash height, and initials the sticker. The sash height at which the average face velocity is 100 fpm is also indicated.
  • Fume hood testing information is recorded in the database maintained at the EH&S Office. It should include Principal Investigator (PI), department, building, room number, hood ID #, date, velocity (fpm) and tester initials.

4. Fume Hood Certification Ratings Interpretation
The fume hood certification is characterized as follows:

  • Certified: A hood is considered certified when the average face velocity at 12” working sash height is between 80 – 120 fpm.
  • Not Certified: If the face velocity at 12” working sash height is below 80 fpm or above 120 fpm the hood is considered not certified. A DO NOT USE sticker is placed on the sash and the PI is advised not to use the hood.

5. Fume Hood Failure Procedures
a) User Responsibility
i. If it is suspected that a fume hood is not working properly, work inside the hood should stop immediately and the problem reported to:

  • Principal Investigator or Laboratory Manager
  • MS Facilities at (212)-854-2222.
  • CUMC Facilities at (212)-305-7367.
  • LDEO Facilities at (845)-365-8600.
    • LDEO Security & Safety at (845)-365-8865.
  • Nevis at (914)-591-9244.
  • EH&S at MS at (212)-854-8750.
  • EH&S at CUMC at (212)-305-6780.

ii. Notify others in the area that the fume hood is not operating and cannot be used, and post a “Do Not Use” sign on the hood. The PI must strictly enforce this.
iii. Close/cover any opened/exposed chemical containers or radioactive materials.  It may be necessary to remove all chemicals and equipment from a hood to allow access for repair.
iv. Although rare, hood repair may require extended downtime if major parts (e.g. fan motor) needs replacement.  Procedures that must be conducted within a hood must be relocated to another working hood during this time.
v. When repair is completed, the hood is recertified for use by EH&S.

b) Department of Environmental Health & Safety (EH&S)

i. Assists in the communication between Facilities Operations (FO) and PI or designee on status of hood inspection or repair.
ii. Provides necessary clearance to FO for repair.
iii. Re-certify fume hood when repair is complete.
iv. Gives clearance for use after retesting/recertification.

c) Facilities Management/Operations (FO)

i. Lockout and tagout individual hoods prior to conducting investigations. Ensure that all non-CU contractors follow fume hood lockout/tagout procedures.
ii. Investigates hood failure through a review of the entire system (e.g., motor, belts, fan unit and electrical connections).
iii. Notifies PI and research personnel of the affected lab and EH&S of the hood problem and gives an estimated time necessary for repair. Posts affected hood with "Do Not Use" sign (if not already posted by EH&S).
iv. Removes lockout of hoods when the hood is returned to service and informs relevant individuals.

6. Fume Hood Scheduled Maintenance:
FO shall perform annual checks on fume hood and ductwork as a part of preventive maintenance.
a) FO shall provide advance notification to relevant PIs and lab personnel, and EH&S of the planned interruption of fume hood service and tag the affected fume hoods with “Do Not Use” signs.  During this time, no procedures shall be conducted inside the affected fume hoods.  If procedures cannot be interrupted or relocated to another fume hood during this time, the PI/lab personnel shall inform FO of this conflict and schedule a mutually convenient time for preventive maintenance to be conducted.
b) Fume hood service interruption notices shall include:

i.  Date/time of shutdown
ii. Fan Motor # to be shutdown
iii. Reactivation date/time
iv. Number to call for further information

c) Once scheduled, the PI and lab personnel shall make necessary arrangements to conduct procedures requiring local exhaust ventilation elsewhere, or suspend these activities until service is restored.
d) FO shall lockout and tagout affected hoods so that they cannot be used during this time. All hazardous materials inside the hoods must be in closed containers or removed.
e) Once FO has completed maintenance, the lockout device(s) shall be removed and EH&S notified.
f) EH&S shall reevaluate such hoods and give clearance for use when maintenance is complete.

7. Roof Work

Chemical fume hood exhaust stacks are located on the roof, which may release chemical contaminants outdoors.  Fume hood exhaust ducts terminate just above the roofline in many cases.  Working near these outlets could potentially expose workers to hazardous chemicals, albeit in extremely dilute concentrations.  If maintenance/repair work must be done on the roof of any building containing hood exhaust(s), FO must first notify the PI and EH&S to provide them with information regarding chemicals used in their fume hoods.

8. Fume Hood Flow Monitoring Devices
New and reconditioned hoods should be equipped with an airflow-monitoring device that provides an indication of the face velocity.  For uniformity the selection must be reviewed by EH&S.  The device should be checked and recalibrated by EH&S annually at the time of recertification. For any damaged devices Facilities should be contacted for repair or replacement.

9. Fume Hood Safe Work Practices
Lab personnel shall employ work practices that minimize/eliminate their exposures when working with hazardous materials in fume hoods:

  • Lab personnel should not place their upper body in the fume hood except during initial setup of equipment inside the hood, before any hazardous materials have been placed inside the hood.
  • Hazardous materials should be placed > 6” inside the hood for proper containment of chemical vapors.
  • Hoods should not be used for permanent storage of hazardous materials.
  • Equipment inside the hood should be placed so as to not block airflow through slots in the baffle.
  • Equipment that could be sources of emission (including in case of breakage) should be placed > 6” inside the hood.
  • The hood sash or panels should be lowered to the lowest (comfortable) working height, usually 12”.  Fully opening the sash lowers the face velocity to the point of ineffectiveness.
  • The hood sash or panels shall not be removed except for initial experimental setup and before hazardous chemicals are placed in the hood.
  • Each hood shall be posted with a sticker showing the date of last certification. If the hood failed the performance test, it shall be taken out of service until repaired, or posted with a restricted use notice.
  • Filters to remove contaminants, though rarely used for specific operations like volatile radioactive materials, shall be maintained as recommended by the manufacturer.

10. Removing Hoods From Service

When a chemical fume hood is to be removed from service, the PI must ensure that all hazardous materials have been removed and the hood has been properly decontaminated.  If radioactive materials have been used in the hood, the Radiation Safety Officer must survey the fume hood for radioactive contamination.  After decontamination and final survey, clearance for removal is given by EH&S.

B. Ductless Fume Hood Use Policy

Ductless fume hoods are designed to remove hazardous fumes and vapors from the work area by passing the exhaust air through an adsorbent, such as an activated charcoal filter. However, they do not provide adequate face velocity and require constant attention. In many cases, the filter is designed for a specific chemical and will not protect against the variety of chemicals used in a typical research laboratory. A "breakthrough" and desorption of vapors from the adsorbent may also expose personnel. In addition, it is expensive to replace expended filters and to dispose of them as hazardous waste.

It is strongly recommended NOT to use ductless fume hoods. Under extremely rare and unusual circumstances, when used for small amounts of low-toxicity chemicals, the hood should be clearly labeled by the PI to indicate that it might not provide suitable protection from exposure to hazardous chemical vapors. EH&S does NOT certify ductless fume hoods, the user must follow the manufacturer’s recommendations to change and dispose of filters.

INQUIRIES/REQUESTS
Morningside (MS) Campus:  EH&S at (212)-854-8749.
Columbia University Medical Center (CUMC) Campus: EH&S at (212)-305-6780.
Lamont (LDEO) Campus: Security & Safety (845)-365-8860.
Nevis Campus: (914)-591-9244.

RESPONSIBILITIES

PI

  • Inform all lab personnel if hood is not working.
  • Place a Do Not Use sticker on the hood if it is not working properly.
  • Contact FO for repair or air flow adjustment.

Facilities:

  • Repair and adjust adequate flow rate of CFH.
  • Provide adequate preventive maintenance of all CFH
  • Ensure personnel safety when repairing CFH.
  • Contact EH&S to do re-certification after repair or adjustment of CFH

EH&S

  • Certify all CFH annually.
  • Issue Clearance before CFH repairs.
  • Inform PI and FO if a CFH fails certification.
  • Re-certify CFH after repairs or adjustment.

REFERENCES:

  • ANSI/AIHA Z9.5-2003, American National Standard for Laboratory Ventilation.
  • ACGIH’s Industrial Ventilation: A Manual for Recommended Practice.
  • RCNY Chapter 10, Chemical Laboratories, 1992
  • ANSI/ASHRAE 110-1995 Method of Testing Performance of Laboratory Fume Hoods.

ATTACHMENTS:
A. Testing Procedure
B. Sample Placard
C. Certification Sticker

ATTACHMENT – A

Face Velocity Measurement Procedure

Average face velocity will be determined by measuring air velocity at evenly distributed points in the plane of the hood face in the following manner:

  1. The sash is placed at the lowest working height, usually twelve inches. The plane of the hood face is divided into (at least) three sections equal in area. Face velocity is measured at the center of each section. The hood face velocity is the average velocity of these measurements.
  2. The tester will place certification sticker on the front of the hood, recording the test date, face velocity at a 12” sash height and initials the sticker. The sash height at which the average face velocity is 100 fpm is also indicated.
  3. Fume hood testing information is recorded in the database maintained at the EH&S Office. It should include Principal Investigator (PI), department, building, room number, hood ID #, velocity (fpm) and tester.
  4. If fume hood is not working according to the specifications, the PI or Laboratory Manager are to be instructed to clear the fume hood so that EH&S can provide Clearance for Facilities repair or adjustment.
  5. Facilities should be contacted with a priority for adjustment and faxed a Clearance.
  6. Upon adjustment or repair, and notification by Facilities, EH&S is to verify the fume hood velocity (minimum average 100 FPM @12 inches) and provide certification.
  7. Monitoring results are to be entered into the database.

ATTACHMENT - B

Sticker to be Placed When Hood is Not Working

DANGER

HOOD
IS NOT WORKING
DO NOT USE

 

CALL FACILITIES AT

MS Campus - (212) – 854 - 2222
CUMC Campus - (212) –305 – 7367
LDEO Campus – (845)-365-8860
Nevis Campus – (9140 591 - 9244

CALL EH&S

MS Campus  -  (212) – 854 - 8749
CUMC Campus – (212) – 305 - 6780

ATTACHMENT -  C

Fume Hood Certification Sticker

Fume Hood Certification

Hood #  __________

 

Date        Operating Height (in)                          Avg. Velocity                       Avg. Velocity                       Inspected By
                (Avg. 100 FPM)                                    Full Open                               (12” Open)
_____    ________________                           ________________           _______________             ____________

_____    ________________                           ________________           _______________             ____________

_____    ________________                           ________________           _______________             ____________

_____    ________________                           ________________           _______________             ____________

_____    ________________                           ________________           _______________             ____________

_____    ________________                           ________________           _______________             ____________
Do not use Perchloric Acid in this Hood                                         Hood flow rate should be 100 FPM at 12” sash height

Hood should be certified annually. If any question, call EH&S (212) 854 – 8749 at Morningside or (212) 305 – 6780 at Columbia University Medical Center (CUMC).

This sticker must be placed on each fume hood and completed at the time of certification

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