Waste anesthetic gases are small amounts of volatile anesthetic gases that leak from the patient's anesthetic breathing circuit* into the air of operating rooms during delivery of anesthesia. These gases may also be exhaled by patients recovering from anesthesia. Waste anesthetic gases include both nitrous oxide and halogenated anesthetics such as halothane, enflurane, isoflurane, desflurane, sevoflurane, and methoxyflurane (no longer used in the United States). The halogenated anesthetics are often administered in combination with nitrous oxide. Nitrous oxide and some of the halogenated anesthetics may pose a hazard to hospital workers. The purpose of this brochure is to do the following: 1. Increase awareness about the adverse health effects of waste anesthetic gases; 2. Describe how workers are exposed to waste anesthetic gases; 3. Recommend work practices to reduce these exposures; 4. Identify methods to minimize leakage of anesthetic gases into the work environment.