Prudent execution of experiments requires not only sound judgment and an accurate assessment of the risks involved in laboratory work, but also the selection of appropriate work practices to reduce risk and protect the health and safety of the laboratory workers as well as the public and the environment. Chapter 3 provides specific guidelines to enable laboratory workers to evaluate the hazards and assess the risks associated with laboratory chemicals, equipment, and operations. Chapter 4 demonstrates how to control those risks when managing the inventory of chemicals in the laboratory. How the protocols outlined in Chapter 3 are put to use in the execution of a carefully planned experiment is the subject of Chapter 5.

Chapter 5 presents general guidelines for laboratory work with hazardous chemicals rather than specific standard operating procedures for individual substances. Hundreds of thousands of different chemicals are encountered in the research conducted in laboratories, and the specific health hazards associated with most of these compounds are generally not known. Also, laboratory work frequently generates new substances of unknown properties and unknown toxicity. Consequently, the only prudent course is for laboratory personnel to conduct their work under conditions that minimize the risks due to both known and unknown hazardous substances. The general work practices outlined in this chapter are designed to achieve this purpose.

Specifically, section 5.C describes basic prudent practices that should be employed in all laboratory work with chemicals. These guidelines are the standard operating procedures for all work conducted in laboratories where hazardous chemicals are stored or are in use.

In section 5.D, additional special procedures are presented for work with highly toxic substances. How to determine when these additional procedures are necessary is discussed in detail in Chapter 3, section 3.C. Section 5.E gives detailed special procedures for work with chemicals that pose risks due to biohazards and radioactivity; section 5.F, flammability; and section 5.G, reactivity and explosibility. Special considerations for work with compressed gases are the subject of section 5.H.

Chapter 6 provides precautionary methods for handling laboratory equipment commonly used in conjunction with hazardous chemicals. Chapters 3, 5, and 6 should all be consulted before working with hazardous chemicals.

Four fundamental principles underlie all of the work practices discussed in this chapter:

  • Plan ahead. Determine the potential hazards associated with an experiment before beginning it.

  • Minimize exposure to chemicals. Do not allow laboratory chemicals to come in contact with skin. Use laboratory hoods and other ventilation devices to prevent exposure to airborne substances whenever possible.

  • Do not underestimate risks. Assume that any mixture of chemicals will be more toxic than its most toxic component. Treat all new compounds and substances of unknown toxicity as toxic substances.

  • Be prepared for accidents. Before beginning an experiment, know what specific action to take in the event of the accidental release of any hazardous substance. Know the location of all safety equipment and the nearest fire alarm and telephone, and know what telephone numbers to call and whom to notify in the event of an emergency. Be prepared to provide basic emergency treatment. Keep your co-workers informed of your activities so that they can respond appropriately.

5.B Prudent Planning

The risk associated with an experiment should be determined before the laboratory work begins. The hypothetical question that should be posed before an experiment is, ''What would happen if... ?" For the possible contingencies, preparations should be made to take the appropriate emergency actions. The worker should know the location of emergency equipment and how to use it. He or she should be familiar with emergency procedures and should know how to obtain help in an emergency. Any special safety precautions that may be required should be addressed before the experiment is begun. The consequences of loss of electrical power or water pressure should also be considered.

The physical and health hazards associated with chemicals should be determined before working with them. This determination may involve consulting literature references, Laboratory Chemical Safety Summaries (LCSSs), Material Safety Data Sheets (MSDSs), or other reference materials (see also Chapter 3, section 3.B) and may require discussions with the laboratory supervisor and consultants such as safety and industrial hygiene officers. Every step of the waste minimization and removal processes should be checked against federal, state, and local regulations. Production of mixed chemical-radioactive-biological waste (see Chapter 7, section 7.C.1.3) should not be considered without discussions with environmental health and safety experts.

Many of the general practices applicable to working

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