Drexel University Laboratory Fume Hood Program

I. Overview

A. Background

In order to ensure the health and safety of students, faculty, and other employees in our teaching and research laboratories, the development of a standardized hood maintenance and testing procedure is mandated by the Occupational Health and Safety Administration's (OSHA's) Laboratory Standard (29 CFR 1910.1450)¹. Although the Drexel University Safety Committee has done some research on the accepted methods for maintaining and testing laboratory fume hoods^2-6, much of this document has been liberally "borrowed" from the Harvard University hood maintenance and testing program written by Louis J. DiBerardinis². This should be viewed as recognition of the completeness of his work, rather than a lack of effort on the part of the administration of Drexel University or the members of the Safety Committee.

B. Periodic Review

The ad hoc committee for laboratory fume hoods shall jointly review this document on an annual basis. The ad hoc committee shall include representation from the University Safety & Health Department, Facilities Management Department, and academic departments that utilize fume hoods.

II. Responsibilities

A. University Safety & Health Department

The University Safety & Health Department will:

· Perform an airflow survey on all university fume hoods at least annually.

· Perform an airflow survey on laboratory fume hoods at the request of a user.

· Report the results of any fume hood survey to the departmental Chemical Hygiene Officer in written form.

· Report unsafe hoods to the user and Facilities Management Department immediately via fax 215-895-6754 and work order.

· Perform a follow-up airflow survey promptly after appropriate repairs are completed on those fume hoods found unsafe.

· Advise on the selection and installation of new fume hoods and advise on the relocation of existing hoods.

· Perform an airflow survey on newly installed, renovated, or rebuilt/relocated fume hoods before they are used by the user.

· Place a lockout device on fume hoods that are considered unsafe due to the airflow survey. The lockout device will be used to ensure the safety of the user and will remain in place until appropriate repairs are made.

B. University Facilities Management Department

The University Facilities Management Department will:

· Within 24 hours of notification of an unsafe hood by a user, departmental Chemical Hygiene Officer or the Safety & Health Department, evaluate the hood system and make appropriate repairs. Upon completion of the repair, notify both the departmental Chemical Hygiene Officer and the Safety & Health Department that the hood is repaired. If the repair requires more than one working day to complete, the user must be notified that the hood is not repaired and should be apprised as to how long it will take to obtain parts, etc., and the hood should remained locked out.

· During maintenance, the hood should be locked and tagged out to indicate that the hood is undergoing maintenance.

· Facilities Management must advise on the selection and supervise installation of new and/or rebuilt fume hoods and approve the relocation of existing hoods.

· Follow the routine preventive maintenance, notification, and hood testing procedures described below.

C. Departmental Chemical Hygiene Officer (CHO)

The departmental Chemical Hygiene Officer (CHO) will:

· Report questionable operations of a laboratory fume hood to the Safety and Health and Facilities Management Departments.

· Post fume hood safety procedures on all fume hoods.

· Serve as the contact person for notification of any fume hood related issues.

· Consult with the Safety & Health and Physical Plant Departments before a new hood is ordered, installed, or an existing hood is renovated or relocated.

D. Laboratory Supervisor

The Laboratory Supervisor will:

· Ensure that the laboratory work carried out in the laboratory fume hood is appropriate for the type of hood available and the quality of ventilation present.

· Report questionable operation of a laboratory fume hood to the departmental CHO immediately.

E. Laboratory Hood User

The Laboratory Hood User will:

· Follow proper procedures when using the laboratory fume hood. See the article by Mikell and Fuller entitled "Good Hood Practices for Safe Hood Operation"¹⁰ and the American Chemical Society publication Safety in Academic Chemistry Laboratories, 5th ed.¹¹, for suggestions on proper hood techniques.

· Report questionable operation of a laboratory fume hood to the department CHO immediately.

· Avoid using the hood for chemical storage.

III. Types of Fume Hoods;:

The following information concerning types of laboratory fume hoods available is abstracted from the SAMA Standard for Laboratory Fume Hoods⁷. The majority of laboratory fume hoods have one or two (depending on the size) vertical sliding sashes (i.e., they move up and down). Some hoods are equipped with horizontal sliding sashes (i.e., they move left and right).

A. Conventional Hood

All air enters through the hood opening as defined by the bottom of the sash, sides of the hood, and the work surface. As the viewing sash is lowered both the static pressure loss and air speed increase as the volume of air being exhausted decreases. High face velocities are to be expected with the sash in the near closed position.

B. Conventional Bypass Hood

Bypass-type fume hoods incorporate an automatic compensating opening which functions as the hood sash is closed. Air drawn through the bypass passes through the hood interior to dilute and exhaust generated fumes. The bypass limits the face velocity, increases and maintains a relatively constant exhaust volume as the hood sash is closed. The bypass is usually located directly above the hood sash.

C. Auxiliary Air (Induction) Hood

The auxiliary air system functions to reduce the consumption of conditioned room air.

· With the hood sash open, the auxiliary air shall be introduced exterior to the fume hood, enter the fume hood through the hood face, and be distributed across the face area prior to its passage into the hood.

· With the hood sash closed, the auxiliary air shall be introduced into the fume hood interior in such a manner as to aid in the dilution of heat and fumes generated in the work area.

Although the auxiliary air is brought directly from the outside of the laboratory building, provision should be made to condition the air during extremely hot or cold periods.

D. Radioactive Hood

Any of the above hoods can be used for radioactive materials, provided that:

· The fume hood is properly labeled prior to use with radioactive materials.

· The interior work surfaces should be constructed from non-porous or sealed materials that preclude adsorption of radioactive material and shall resist the corrosive action of chemicals used in this work (usually means use of stainless steel). All seams and joints in the work surface and superstructure should be welded, sealed or soldered to eliminate pockets, cracks or crevices that would permit a buildup of radioactive materials.

· The work surface shall be watertight and dished or furnished with a raised bar across the front edge to contain spills and cleaning liquids.

· The work surface should be properly reinforced to support lead shielding and shielded containers. The load bearing capacity shall be 200-pounds/square foot minimum up to a total weight of 1000 pounds per fume hood.

· Some types of radioactive materials require a filter at the hood outlet; these should be regularly inspected by the University Radiation Safety Officer.