and paying attention to monitoring and decontamination.

  • Keep an accurate inventory of radioisotopes.

  • Record all receipts, transfers, and disposals of radioisotopes.

  • Record surveys.

  • Check workers and the work area each day that radioisotopes are used.

  • Minimize radioactive waste.

  • Plan procedures to use the smallest amount of radioisotope possible.

  • Check waste materials for contamination before discarding.

  • Place only materials with known or suspected radioactive contamination in appropriate radioactive waste containers.

  • Do not generate multihazardous waste (combinations of radioactive, biological, and chemical waste) without first consulting with the designated radiation and chemical safety officers.

(See Chapter 7 for more information on waste and disposal.)

5.F WORKING WITH FLAMMABLE CHEMICALS

All laboratory personnel should know the properties of chemicals they are handling as well as have a basic understanding of how these properties might be affected by the variety of conditions found in the laboratory. As stated in section 5.B, Laboratory Chemical Safety Summaries (LCSSs) or other sources of information should be consulted for further information such as vapor pressure, flash point, and explosive limit in air. The use of flammable substances is common, and their properties are also discussed in Chapter 3, section 3.D.

General prudent practices include minimizing the amounts used, storing chemicals properly, keeping appropriate fire extinguishing equipment readily available, physically separating flammable materials from other operations and sources of ignition, properly grounding static sources of ignition, and using the least hazardous alternative available.

Ignition sources should be eliminated from any area where flammable substances are handled. Open flames, such as Bunsen burners, matches, and smoking tobacco, are obvious ignition sources. Gas burners should not be used as a source of heat in any laboratory where flammable substances are used. Less obvious ignition sources include gas-fired space heating or water-heating equipment and electrical equipment, such as stirring devices, motors, relays, and switches, which can all produce sparks that will ignite flammable vapors. Because the location of this equipment is often fixed, operations with flammable substances may have to be carried out elsewhere.

Even low-level sources of ignition, such as hot plates, steam lines, or other hot surfaces, can provide a sufficiently energetic ignition source for the most flammable substances in general laboratory use, such as diethyl ether and carbon disulfide (see Chapter 3, section 3.D.1.3). Flammable substances that require low-temperature storage should be stored only in refrigerators designed for that purpose. Ordinary refrigerators are a hazard because of the presence of potential ignition sources, such as switches, relays, and, possibly, sparking fan motors, and should never be used for storing chemicals. When transferring flammable liquids in metal containers, sparks from accumulated static charge must be avoided by grounding.

Fire hazards posed by water-reactive substances such as alkali metals and metal hydrides, pyrophoric substances such as metal alkyls, strong oxidizers such as perchloric acid, and flammable gases such as acetylene require procedures beyond the standard prudent practices for handling chemicals described here (see sections 5.C and 5.D) and should be researched in LCSSs or other references before work begins. In addition, emergency response to incidents involving these substances must take their special hazards into account.

5.F.1 Flammable Materials

The basic precautions for safe handling of flammable materials include the following:

  • Handle flammable substances only in areas free of ignition sources. Besides open flames, ignition sources include electrical equipment (especially motors), static electricity, and, for some materials (e.g., carbon disulfide), even hot surfaces. Check the work area for flames or ignition sources before using a flammable substance. Before igniting a flame, check for the presence of a flammable substance.

  • Never heat flammable substances with an open flame. Preferred heat sources include steam baths, water baths, oil and wax baths, salt and sand baths, heating mantles, and hot air or nitrogen baths.

  • Ventilation by diluting the vapors until they are no longer flammable is one of the most effective ways to prevent the formation of flammable gaseous mixtures. Use appropriate and safe exhaust whenever appreciable quantities of flammable substances are transferred from one container to another, allowed to stand in open containers, heated in open containers, or handled in any other way. In using dilution techniques, make certain that equipment (e.g., fans) used to pro-



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