cals or to start a siphon; pipetting should never be done by mouth. Hands should be washed with soap and water immediately after working with any laboratory chemicals, even if gloves have been worn.

5.C.2.3 Avoiding Inhalation of Hazardous Chemicals

Toxic chemicals or compounds of unknown toxicity should never be smelled. Procedures involving volatile toxic substances and operations involving solid or liquid toxic substances that may result in the generation of aerosols should be conducted in a laboratory hood. Dusts should be recognized as potentially contaminated and hazardous. Hoods should not be used for disposal of hazardous volatile materials by evaporation. Such materials should be treated as chemical waste and disposed of in appropriate containers in accord with institutional procedures.

The following general rules should be followed when using laboratory hoods:

  • For work involving hazardous substances, use only hoods that have been evaluated for adequate face velocity and proper operation. Hood operation should be inspected regularly, and the inspection certified in a visible location.

  • Keep reactions and hazardous chemicals at least 6 inches behind the plane of the hood sash.

  • Never put your head inside an operating laboratory hood to check an experiment. The plane of the sash is the barrier between contaminated and uncontaminated air.

  • On hoods where sashes open vertically, work with the hood sash in the lowest possible position. On hoods where sashes open horizontally, position one of the doors to act as a shield in the event of an accident in the hood. When the hood is not in use, keep the sash closed to maintain laboratory airflow.

  • Keep hoods clean and clear; do not clutter with bottles or equipment. If there is a grill along the bottom slot or a baffle in the back of the hood, clean them regularly so they do not become clogged with papers and dirt. Allow only materials actively in use to remain in the hood. Following this rule will provide optimal containment and reduce the risk of extraneous chemicals being involved in any fire or explosion. Support any equipment that needs to remain in hoods on racks or feet to provide airflow under the equipment.

  • Report suspected hood malfunctions promptly to the appropriate office, and make sure they are corrected. Post the name of the individual responsible for use of the hood in a visible location. Clean hoods before maintenance personnel work on them.

(See Chapter 8, section 8.C, for more information on hoods.)

5.C.2.4 Avoiding Injection of Hazardous Chemicals

Solutions of chemicals are often transferred in syringes, which for many uses are fitted with sharp needles. The risk of inadvertent injection is significant, and vigilance is required to avoid that accident. Needles must be properly disposed of in "sharps" containers. Use special care when handling solutions of chemicals in hypodermic syringes.

5.C.2.5 Minimizing Skin Contact

Wear gloves whenever handling hazardous chemicals, sharp-edged objects, very hot or very cold materials, toxic chemicals, and substances of unknown toxicity. The following general guidelines apply to the selection and use of protective gloves:

  • Wear gloves of a material known to be resistant to permeation by the substances in use. Wearing the wrong type of glove can be more hazardous than wearing no gloves at all, because if a chemical seeps through, the glove can hold it in prolonged contact with the wearer's hand.

  • Inspect gloves for small holes or tears before use.

  • Wash gloves appropriately before removing them. (Note: some gloves, e.g., leather and polyvinyl alcohol, are water-permeable.)

  • In order to prevent the unintentional spread of hazardous substances, remove gloves before handling objects such as doorknobs, telephones, pens, and computer keyboards.

  • Replace gloves periodically, depending on the frequency of use and their permeation and degradation characteristics relative to the substances handled.

(For more information, see OSHA Personal Protective Equipment Standard (29 CFR 1910.132-138) regarding hand protection.)

5.C.2.6 Clothing and Protective Apparel

Long hair and loose clothing or jewelry must be confined when working in the laboratory. Unrestrained long hair, loose or torn clothing, and jewelry can dip into chemicals or become ensnared in equipment and moving machinery. Clothing and hair can catch fire. Sandals and open-toed shoes should never be worn in a laboratory in which hazardous chemicals are in use.

It is advisable to wear a laboratory coat when work-

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