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Waste Anesthetic Gases (WAG)

Anesthetic gases such as isoflurane and sevoflurane are commonly used in laboratory animal research protocols.  Possible health effects of overexposure to anesthetic gas may include, but are not limited to:  

  • Acute effects: Drowsiness, irritability, depression, headaches, dizziness, and nausea, as well as problems with coordination, audiovisual ability, and judgment. 

  • Chronic effects: Liver and kidney disease, and adverse reproductive effects. 

Always work in a well-ventilated area with at least 6 room air changes per hour (ACH) regardless of the gas scavenging methods in use.  


All staff, faculty, students, or others that work or spend time in; laboratories, operating rooms, recovery rooms, radiology, etc. where anesthetic gases are used, stored, or transported are covered under this program.  Environment, Health and Safety can assist campus groups by providing a variety of health and safety services.  


University Administration

University Administrators provide senior management support for implementing the EHS Waste Anesthetic Gas (WAG) Program and ensure that resources are allocated for implementing these procedures.

Environment, Health and Safety

The Department of Environment, Health and Safety develops and oversees the implementation of the EHS Waste Anesthetic Gas (WAG) program by:

  • Providing oversight, leadership, and technical expertise to develop a safety program that provides awareness training, risk assessments, technical advice, exposure monitoring, and emergency response.  Emergency response includes responding to worker exposures, addressing leaks and spills, providing response to spills and/or clean up, and incident investigations.

  • Communicating the program to all areas of campus, where applicable.

  • Utilizing industry accepted sampling protocols and defined limits:

    • The American Conference of Governmental Industrial Hygienists (ACGIH) 50 ppm standard for isoflurane.

    • The National Institute for Occupational Safety and Health (NIOSH) 2 ppm standard for other halogenated anesthetics, such as sevoflurane.

  • Maintaining all sampling equipment and instrumentation that is used in WAG sampling and emergency response.

  • Maintaining all records for exposure monitoring, reports, and recommendations.

Research or Clinical Personnel

All Cornell research or clinical personnel that fall under this program are responsible for:

  • Completing required trainings:

  • Using anesthetic gases in a manner consistent with the design of the machine and the scavenging system used.  The employee shall ask their supervisor for assistance in the event of problems or difficulties.

  • Checking all equipment prior to use for leaks and setup integrity, and reporting problems to your supervisor immediately.

  • Following all manufacture recommendations regarding gas delivery and scavenging systems.  

  • Weighing charcoal canisters before and after each use when charcoal canisters are used.

  • Reporting any incidents related to the use of anesthetic gases. 

  • Participating in personal monitoring when requested by EHS.                                              

Principal Investigators (PIs) and Supervisors

Cornell University PIs and Supervisors support the Waste Anesthetic Gas safety program by:

  • Ensuring that all employees complete required trainings:

  • Ensuring this written program and all components of are followed.

  • Ensuring personal monitoring is completed when requested by EHS.

  • Following up on any reported concerns by users of the anesthetic gas systems.

  • Following up on any incidents related to the use of anesthetic gas and implementing changes identified by EHS.

Engineering Controls

Work in a certified chemical fume hood or ducted biosafety cabinet (BSC) for best WAG capture: 

                Active Circuit 

                Method 1a – A vacuum pump device in the breathing system.  Devices (e.g., EVAC-4, SOMNI                    EPS-3, VetEquip cube) are ducted to the building exhaust system. 

                Method 1b – A vacuum pump device in the breathing system.  Devices are connected to an                    activated charcoal canister. 

                Passive Circuit with Active Scavenging 

                Method 2 – Localized exhaust ventilation (e.g., Snorkel, Fume Hood, Downdraft Table) is                          positioned near the breathing system to draw and/or capture WAG.  An activated charcoal                      canister is used for gas deactivation. 

Other methods may be approved by EHS on an individual basis after monitoring has been completed. 

Safe Work Practices

Preparing for anesthetic gas use: 

  • Inspect anesthesia equipment and the scavenging system.  

  • Verify equipment (e.g., fume hood and vaporizer) is currently certified and in proper working condition.  Preform a pressure test to check for leaks, defects, and damage in anesthesia equipment (including hoses and valves) and the scavenging system. 

  • Fill vaporizer using an anti-spill bottle adaptor.   

Preparing charcoal canisters for use: 

  • Charcoal canisters must be weighed before and after each use to ensure they are within the manufacturer’s specified limits (e.g., <50 grams above the initial weight or 12 hours of use); record the weight on the canister. 

  • Confirm that the canister is correctly plugged into the breathing system.  Use charcoal canisters according to manufacturer’s recommendations. 

  • Ensure the canister holes are not obstructed and that canisters are upright. 

For anesthetic inductions: 

  • Open-drop anesthetic procedures are not recommended and must be conducted within a chemical fume hood or ducted biosafety cabinet (BSC). 

  • Do not turn on the vaporizer until the animal is in the induction chamber. 

  • Before retrieving the anesthetized animal, purge the induction chamber with oxygen for 5 to 15 seconds prior to opening the chamber. 

  • Keep the vaporizer turned off until the animal is properly positioned in the nose cone. 

  • Apply the appropriate dosage of anesthesia for the length of the procedure. 

  • Frequently inspect the condition of the induction chamber seal and the scavenging system for leaks. 

For surgical procedures: 

Minimize WAG leakage from the nose cone by selecting the best fitting nose cone. To optimize the fit, nose cone diaphragms are often available from the manufacturer.  Contact CARE for assistance ordering equipment.   

  • Oxygen flow rate and anesthetic concentration should be as low as possible to minimize anesthetic gas usage. 

  • Keep WAG scavenging devices such as snorkels positioned as close as possible to potential points of release (e.g., at animal nosecone). 

  • Keep the individual’s breathing zone away from the animal nosecone. 

  • Turn off the vaporizer before taking the animal out of the nose cone. 

For imaging procedures: 

  • Close or plug the nose ports inside the imaging machine if they are not in use. 


Measure human exposure to WAG whenever:   

  • There is a new setup, or an existing setup has not been used within one year. 

  • Anesthetic gas can be smelled. 

  • People are experiencing fatigue or headaches when using the anesthetic equipment. 

Human exposure monitoring is conducted by EHS and results will be referenced against American Conference of Government Industrial Hygienists (ACGIH) Guidelines for Isoflurane (50 ppm) and NIOSH Guidance for other halogenated compounds (2 ppm).  

EHS will be monitoring all set-ups a minimum of once every three years.  

Personal Protective Equipment

  • Standard PPE for anesthetic gas users is safety glasses, nitrile gloves, and lab coats.

  • If working in a vivarium, follow any additional PPE requirements such as gowns.

  • Additional PPE may be needed if additional hazards are present during use.


Whenever transporting chemicals by hand, always use a secondary container such as a rubber carrying bucket, plastic bucket, or a 5-gallon pail.  

If necessary, a small amount of packing material (shipping peanuts, vermiculite, or cardboard inserts), that is compatible with the chemical, should be used to prevent bottles from tipping over or breaking during transport.  

Emergency Preparedness

First Aid 

  • For medical emergencies, call 911 from a campus phone or (607) 255-1111 from a cell phone. 

  • Know where the nearest emergency eyewash and safety shower are located and use if needed. 

For spills outside of a fume hood or hard-ducted biosafety cabinet: 

  • Leave the room and call (607) 255-1111.  Provide your name, location, and the chemical for assistance with spill clean-up. 

For spills inside a fume hood: 

  • Notify other people in the area that a spill has occurred.  Prevent others from entering the spill zone.  The first priority is always to protect yourself and others. 

  •  Stop the source of the spill if possible, and if safe to do so.   

  • Try to prevent spilled chemicals from entering waterways by building a dike around access points (sink, cup sinks) with absorbent material if you can safely do so. 

  • Slowly add absorbent material on and around the spill and allow the chemical to absorb.  Apply enough absorbent to completely cover the spilled liquid.  Sweep up the absorbed spill from the outside towards the middle.  Scoop up and deposit in a leak-proof container. 

  • Label the container and dispose of through the hazardous waste management program. 

  • Wash the contaminated surface with soapy water. 

  • Report the spill to your supervisor, submit an injury-free incident report and restock any supplies that you may have used from any spill kits. 

Waste Management

  • Manage unused/expired anesthetics and used charcoal canisters as hazardous waste.

  • Empty isoflurane bottles can be disposed of as non-hazardous waste.  Deface labels and discard in the regular trash.

Equipment Maintenance

  • Anesthesia machines and vaporizers are to be calibrated and certified as recommended by the manufacturer.  Contact CARE ( to schedule annual inspection / certification of anesthetic equipment. 

  • Frequently inspect the condition of the induction chamber seal and the scavenging system for leaks. 

Standard Operating Procedures (SOPs)

  • Establish lab-specific Standard Operating Procedures (SOPs) for routine use, inspection, and maintenance of anesthesia and scavenging systems.

  • Train new users using the SOP and document the on-site training.

For questions on Waste Anesthetic Gas Safety, set-up review, or personal monitoring, please contact askEHS