Waste Anesthetic Gases

Waste anesthetic gases (halogenated hydrocarbons and/or nitrous oxide) pose potential acute and chronic health hazards (review material safety data sheets). Exposure to trace amounts of waste anesthetic gases can affect personnel performance and increasing the risk of injury. Such exposure typically occurs during initial setup and checking of the anesthesia and/or scavenging system, from leaks around the face mask or in the anesthesia system, when purging the system at the end of a procedure and during recovery from anesthesia.

Controlling exposure to waste anesthetic gases

Exposure to waste anesthetic gases can be effectively controlled through judicious use of engineering controls, administrative controls, safe work practices, environmental monitoring and hazard communication and training.

Engineering Controls

  • Scavenging systems collect, remove and properly dispose of waste anesthetic gases away from buildings and are the primary and preferred method for protection against exposure. Such systems can remove up to 90% of the waste anesthetic gases; and may be coupled with an activated charcoal absorption system for halogenated hydrocarbons. Active evacuation involves a negative pressure system or fume hood. Passive evacuation relies on positive pressure generated by oxygen flow, during exhalation or compression of the breathing system reservoir bag
  • Building heating, ventilation and air conditioning (HVAC) systems provide additional protection by diluting out and removing residual gases not captured by the scavenging systems. Non-recirculating HVAC systems can reduce waste anesthetic gases in the recovery area.
  • Properly designed anesthesia delivery masks capture exhaled anesthetic gases

Administrative Controls

  • Encourage a culture of safety
  • Write and follow standard operating procedure for the anesthetic machine, related equipment and scavenging system for: maintenance and inspection (checkout) before (daily) use with particular attention to potential sources of leaks; and routine preventive maintenance and repairs
  • Document daily and routine maintenance of the system

Safe Work Practices

  • Reduce exposure to waste anesthetic gases by: utilizing scavenging systems; leak-testing equipment; properly fitting face masks; using appropriately sized endotracheal tubes; correctly inflating endotracheal tube cuffs; connecting tubes and fittings properly; using keyed filler systems or bottle adapters with spout; filling vaporizers when few people are around; using low fresh-gas flow rates; turning off the gas prior to removing patient from anesthetic machine; maintaining oxygen flow until the scavenging system is flushed; labeling anesthetic gas appropriately; placing warning signage where occupational exposure can occur; using appropriate personal protective equipment.

Environmental Monitoring

  • Monitoring environmental concentration of anesthetic gases determines effectiveness of the waste gas control program and aids in identifying sources of leaks.
  • Document and retain environmental monitoring results

Hazard Communication and Training

  • Train individuals to use equipment properly and on potential hazards and mitigation procedures.
    1. Describe hazards specific to the anesthetic in use
    2. Provide material safety data sheets
  • Label all canisters, tanks and containers
  • Mitigation procedures include: use of engineering controls, spill containment, safe work practices, personal protective equipment, and use of monitoring devices

Waste anesthetic gases present a potential health hazard to individuals. Installation of a properly functioning, correctly-used and properly-maintained scavenging system can significantly reduce anesthetic pollution and personnel exposure when coupled with safe work practices; an issue of particular concern in the laboratory animal field.

Compiled from the following sources –

Anesthetic gases: Guidelines for Workplace Exposures. Occupational Health and Safety Administration, U.S. Department of Labor.

Waste Anesthetic Gases. U.S. Department of Labor, Program Highlight, Fact Sheet No. OSHA 91-38.

Criteria for a Recommended Standard: Occupational Exposure to Waste Anesthetic Gases and Vapors. DHHS (NIOSH) Publication No. 77-140.

Hazards of Waste Anesthetic Gases. Canadian Center for Occupational Health and Safety.

Control of Waste Anesthetic Gases. The American College of Veterinary Anesthesiologists.

Smith, J.A. (1993). Anesthetic pollution and waste anesthetic gas scavenging. Semin. Vet Med Surg (Small Anim). 8:90-103.

Smith, J.C., Bolon, B. (2002). Atmospheric waste isoflurane concentrations using conventional equipment and rat anesthesia protocols. Contemp Top Lab Anim Sci. 41:10-17.

Smith, J.C., Bolon, B. (2003). Comparison of three commercially available activated charcoal canisters for passive scavenging of waste isoflurane during conventional rodent anesthesia. Comtep Top Lab Anim Sci. 42:10-15.

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