LABORATORY SAFETY MANUAL

Site Map of Manual

Lab Safety Manual
1st Page

Chapter 1
Emergency Response

Chapter 2
General Safety

Chapter 3
Chemical Hygiene Plan

Chapter 4
Radiological Safety

Chapter 5
Biological Hygiene Plan

Chapter 6
Laser Safety

Chapter 7
Administrative Concerns

Chapter 8
Standard & Special Operating Procedures

Chapter 9
Facility Data

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Appendicies

Bibliography

Glossary

Index

On-Campus Contact Information

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1st Rule of Lab Safety

Haz-Waste No-No

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Updated December 1999

General Safety
Section 2.2 - Safety Equipment

F. Ventilation Hoods

Laboratory Hoods

Work that involves hazards and noxious materials which are toxic, odoriferous, volatile or harmful shall be conducted within a laboratory hood. The primary purpose of a laboratory hood is to keep toxic or irritating vapors and fumes out of the general laboratory working area. A secondary purpose is to serve as a shield between the worker and equipment being used when there is the possibility of an explosive reaction. This is done by lowering the sash of the hood.

1. Hood ventilation systems are best designed to have an airflow of not less than 60 ft/min (linear) and not more than 120 ft/min (linear) across the face of the hood. Flow rates of higher than 125 ft/min can cause turbulence problems and are not recommended. If possible, a mark will have been placed on the hood so the sash can be drawn to a point where 100 linear ft/min can be achieved.

2. Avoid creation of strong cross drafts (100 fpm) caused by open doors and windows, air conditioning and/or heating vents, or personnel movement. Drafts will pull contaminants from the hood and into the laboratory. 100 FPM is generally not perceptible (100 fpm is approximately 3 mph, a normal walking pace). Air conditioning and heating vents and personnel traffic all create airflows in excess of 200 FPM, often much higher. Therefore, laboratory activity in the hood area should be minimized while the hood is in use.

3. DO NOT ADJUST BAFFLES unless you have been instructed to do so by your departmental CHO. Do not remove baffles. If ventilation problems develop, contact the Physical Plant Action Desk (4-7154) immediately.

4. When not in use, the sash of the hood should be kept closed. While performing work in the hood, the sliding sash should be kept at the height designated to provide the minimum face velocity required (usually 100 lfm). This will ensure maximum velocity of air flow into the hood and out of the laboratory.

5. Work should be performed as deeply within the fume hood as possible. Equipment, reagents, and glassware should be placed as far back in the hood as is practical without blocking the rear baffle. Solid objects placed at the face of the hood cause turbulence in the air flow. Therefore, each hood should have a clearly marked "safety zone" in which no work should be conducted or equipment placed.

6. ONLY ITEMS NECESSARY TO PERFORM THE PRESENT EXPERIMENT SHOULD BE IN THE HOOD. The more equipment in the hood, the greater the air turbulence and the chance for gaseous escape into the lab.

7. When instrumentation is utilized for a process inside a hood, all instruments should be elevated a minimum of two inches from the hood base to facilitate proper air movement.

8. The purpose and function of a hood is NOT to store chemicals or unused items. The fume hood is not a storage cabinet.

9. Hoods shall not be used as a means of disposing of toxic or irritating chemicals, but only as a means of removing small quantities of vapor which might escape during laboratory operations. If vaporization of large quantities of such materials is a necessary part of the operation, a means of collecting the vapor by distillation or scrubbing should be considered, rather than allowing it to escape through the hood vent. The collected liquid can then be disposed of as a liquid waste.

10. Some hoods are constructed of stainless steel. These are usually "perchloric acid hoods" or "radioisotope hoods." Never use perchloric acid in a hood not designed for that use. Perchloric acid hoods have a wash-down feature which should be used after each use of the hood and at least every two weeks when the hood is not in use. Date of wash-down should be recorded by the laboratory.

11. Always look to assure fan motor power switch is in the "on" position before initiating experiment. Note: Some hoods do not have individual "on/off" switches and remain "on" continuously.

12. Do not use infectious material in a chemical fume hood.

13. Exhaust fans should be spark-proof if exhausting flammable vapors and corrosive resistant if handling corrosive fumes.

14. Controls for all services (i.e., vacuum, gas, electric, water) should be located at the front of the hood and should be operable when the hood door is closed.

15. Radioactive materials may not be used in the hoods without prior approval of the Radiological Safety Officer.

16. An emergency plan should be prepared in the event of ventilation failure or other unexpected occurrence such as fire or explosion in the hood.
    
    ALWAYS ASSURE THE HOOD IS OPERATIONAL BEFORE INITIATING AN EXPERIMENT.

Biological Safety Cabinets

Biological Safety cabinets are among the most effective, as well as the most commonly used, primary containment devices in laboratories working with infectious agents.

Class I and II biological safety cabinets, when used in conjunction with good microbiological techniques, provide an effective partial containment system for safe manipulation of moderate and some high-risk microorganisms.

It is imperative that Class I and II biological safety cabinets are tested and certified in situs, any time the cabinet is moved, and at least annually thereafter. Certification at locations other than the final site may attest to the performance capability of the individual cabinet or model but does not supersede the critical certification prior to use in the laboratory.

As with any other piece of laboratory equipment, personnel must be trained in the proper use of the biological safety cabinets. Of particular note are those activities which may disrupt the inward directional airflow through the work opening of Class I and II cabinets. Aerosol particles can escape the cabinet in various ways. Among these are repeated insertion and withdrawal of workers' arms in and from the work chamber, opening and closing doors to the laboratory or isolation cubicle, improper placement or operation of materials or equipment within the work chamber, or brisk walking past the cabinet while it is in use. Strict adherence to recommended practices for the use of biological safety cabinets is as important in attaining the maximum containment capability of the equipment as is the mechanical performance of the equipment itself. Always decontaminate the hood using procedures adopted by the laboratory after each use or at the end of the work day.

BIOLOGICAL SAFETY CABINETS ARE NOT CHEMICAL FUME HOODS AND SHALL NOT BE USED AS SUCH.

Specialized Local Ventilation

Some instruments such as atomic absorption spectrophotometers (AA's) or inductively coupled argon spectrometers (ICP's) emit small quantities of hazardous materials during use. To prevent excessive accumulations of these materials, each of these instruments should be provided with an individual ventilation exhaust duct (as required by the manufacturer and ASHRAE). Gas chromatography equipment using thermal conductivity detection should be kept in a hood or have a vent over the column outlets.