sometimes be extinguished with a laboratory fire extinguisher, attempt to put out such fires only if you are trained to use that type of extinguisher, confident that you can do it successfully and quickly, and from a position in which you are always between the fire and an exit to avoid being trapped. Do not attempt to extinguish fires of any size if the institution’s policy prohibits this. A fire can spread and surround you in seconds. Toxic gases and smoke present additional hazards. When in doubt, evacuate immediately instead of attempting to extinguish the fire. Only attempt to extinguish fires of any size if the institution’s policy allows.

   Put out fires in small vessels by covering the vessel loosely. Never pick up a flask or container of burning material.

   Extinguish small fires involving reactive metals and organometallic compounds (e.g., magnesium, sodium, potassium, and metal hydrides) with Met-L-X or Met-L-Kyl extinguishers or by covering with dry sand. Apply additional fire suppression techniques if solvents or combustibles become involved. Because these fires are very difficult to extinguish, sound the fire alarms before you attempt to put out the fire.

   In the event of a more serious fire, evacuate the laboratory and activate the nearest fire alarm. When the fire department and emergency response team arrive, tell them what hazardous substances are in the laboratory.

   If a person’s clothing catches fire, douse him or her immediately in a safety shower. The drop-and-roll technique is also effective. Use fire blankets only as a last resort because they tend to hold in heat and to increase the severity of burns by creating a chimney-like effect. Remove contaminated clothing quickly. Wrap the injured person in a blanket to avoid shock, and get medical attention promptly.

6.D WORKING WITH SUBSTANCES OF HIGH TOXICITY

Individuals who work with highly toxic chemicals, as identified in Chapter 4 (see section 4.C, Tables 4.1, 4.2, and 4.3), should be thoroughly familiar with the general guidelines for the safe handling of chemicals in laboratories (see section 6.C). They should also have acquired through training and experience the knowledge, skill, and discipline to carry out safe laboratory practices consistently. However, these guidelines alone are not sufficient when handling substances that are known to be highly toxic and chemicals that, when combined in an experimental reaction, may generate highly toxic substances or produce new substances with the potential for high toxicity. Additional precautions are needed to set up multiple lines of defense to minimize the risks posed by these substances. As discussed in section 6.B, preparations for handling highly toxic substances must include sound and thorough planning of the experiment, an understanding of the intrinsic hazards of the substances and the risks of exposure inherent in the planned processes, selection of additional precautions that may be necessary to minimize or eliminate these risks, and review of all emergency procedures to ensure appropriate response to unexpected spills and accidents. Each experiment must be evaluated individually because assessment of the level of risk depends on how the substance will be used. Therefore, a prudent planner does not rely solely on a list of highly toxic chemicals to determine the level of the risk; under certain conditions, chemicals not on these lists may react to form highly toxic substances.

In general, the guidelines in section 6.C reflect the minimum standards for handling hazardous substances and should become standard practice when handling highly toxic substances. For example, although working alone in laboratories should be avoided, it is essential that more than one person be present when highly toxic materials are handled. All people working in the area must be familiar with the hazards of the experiments being conducted and with the appropriate emergency response procedures.

Use engineering controls to minimize the possibility of exposure (see section 6.D.5). The use of appropriate PPE to safeguard the hands, forearms, and face from exposure to chemicals is essential in handling highly toxic materials. Cleanliness, order, and general good housekeeping practices create an intrinsically safer workplace. Compliance with safety rules should be maintained scrupulously in areas where highly toxic substances are handled. Source reduction is always a prudent practice, but in the case of highly toxic chemicals it may mean the difference between working with toxicologically dangerous amounts of materials and working with quantities that can be handled safely with routine practice. Emergency response planning and training are very important when working with highly toxic compounds. Additional hazards from these materials (e.g., flammability and high vapor pressures) can complicate the situation, making operational safety all the more important.

6.D.1 Planning

Careful planning should precede any experiment involving a highly toxic substance whenever the substance is to be used for the first time or whenever an experienced user carries out a new protocol that



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