Anesthetic Gases

One of the principal goals of general anesthesia is to prevent patients, both human and animal, from feeling pain during surgery. A common method of anesthesia is the purposeful inhalation of a gas that is known to provide general sedative effects and/or induce unconsciousness. These gases can be separated into two categories: Halogenated anesthetic gases/vapors and nitrous oxide. These may be administered in combination to produce surgical levels of anesthesia. Halogenated anesthetic gases/vapors and nitrous oxide are also commonly used during veterinary care or experiments in animal research.

Assay Technology anesthesia delivery
Anesthesia  Delivery
 Assay Technology (

Anesthetic gases and vapors that leak into the surrounding room are considered waste anesthetic gases (WAGs). If equipment is not set up or functioning properly or if the WAG is not properly exhausted or captured via scavenging, or if ventilation not adequate, healthcare workers, researchers, and veterinary staff may be exposed to WAGs. This exposure creates a risk of potentially developing adverse health effects. EH&S has developed this webpage and the document Anesthetic Gases: Safe Use Guidelines to help users of anesthetic gases understand the potential health effects from exposure and provide guidance in minimizing potential exposures.

Potential exposure to WAGs at UW could occur in the following settings:

  • UW Medicine operating rooms or other clinical applications with anesthesia
  • School of Dentistry facilities and UW Medicine-affiliated dental clinics
  • Department of Comparative Medicine (DCM) facilities (vivaria)
  • Washington National Primate Research Center (WANPRC) facilities
  • Research laboratories doing work with animals


Frequently Asked Questions

All work with anesthetic gases must be performed with either dedicated exhaust (e.g., fume hood, local exhaust ventilation) and/or a scavenging system to prevent exposure. Exposures can occur when handling the gases or liquids, leakage from equipment, from the patient or animal breathing circuit during delivery of anesthesia, or as exhaled by the patient or research animal (e.g., during recovery).

Workers may be exposed to waste anesthetic gases when:


  • Leaks occur in the anesthetic breathing machine, breathing system, hoses, and connections.
  • Anesthetic gas seeps over the lip of the patient’s mask or from the tracheal tubing or coupling
  • Patient is mouth-breathing or talking during dental work


  • Inducing anesthesia using liquid anesthetics and induction boxes
  • Opening induction boxes
  • Charcoal canister in scavenging system is saturated

All applications:

  • Anesthetic gases escape during connection of the anesthesia system or scavenging system
  • Filling vaporizers
  • Leaks occur between subject and facemask/nose cone
  • Liquid anesthetics spill
  • Anesthesia system is flushed or purged at end of a procedure
  • Ineffective or poor ventilation system or gas scavenging system

Clinical workers who may be exposed to anesthetic gases include:

  • Anesthesiologists
  • Nurse anesthetists
  • Dentists
  • Dental assistants
  • Dental hygienists
  • Operating-room nurses
  • Operating-room technicians
  • Other operating-room personnel
  • Recovery-room nurses
  • Other recovery-room personnel
  • Surgeons

In animal research environments, the following workers may be exposed to anesthetic gases:

  • Research staff
  • Veterinary staff
  • Animal care technicians

Most anesthetic gases have high odor thresholds. This means that anesthetic gases cannot be detected by their odor until concentrations are very high. For example, halothane cannot be detected by 50% of the general population until the concentration is more than 125 times the National Institute for Occupational Safety and Health (NIOSH) recommended exposure limit. Therefore, workers should never rely on odor as a warning of potential exposure to anesthetic gases.

Specific anesthetic gases and liquids used at UW are listed below. At room temperature, nitrous oxide is a gas. Mixed with oxygen, it is commonly used for sedation and pain relief in dentistry. The halogenated anesthetic agents are volatile liquids that are vaporized and mixed with other gases prior to inhalation by the patient or subject before or during surgery. Other gas mixtures always include oxygen or air but may also include gases such as nitrous oxide.

  • Nitrous oxide
  • Isoflurane
  • Halothane
  • Desflurane
  • Sevoflurane

Washington state has established permissible exposure limits for nitrous oxide (WAC 296-841-20025). Recommended exposure limits were established (1977) by NIOSH and the American Conference of Governmental Industrial Hygienists (ACGIH) (1989) for nitrous oxide and certain halogenated anesthetic gases. Refer to the document Anesthetic Gases: Safe Use Guidelines for more information.

The specific health effects for nitrous oxide and the halogenated anesthetic gases are summarized below. An acute exposure is defined as a short-term exposure (i.e., minutes to days) to a relatively high concentration of an anesthetic gas. A chronic exposure includes long term exposures (i.e., months to years) to relatively low concentrations of anesthetic gases.

Nitrous Oxide

Acute exposure can cause:

  • Lightheadedness
  • Shortness of breath

Chronic exposure has been linked to:

  • Reproductive effects
  • Neurologic disease
  • Liver/kidney disease

Halogenated Anesthetic Gases

Acute exposure can cause:

  • Central nervous system effects (headache, drowsiness, nausea, irritability)
  • Transient blurring of vision
  • Difficulties with judgement and coordination
  • Liver and kidney disease

Chronic halogenated anesthetics exposure has been linked to:

  • Reproductive effects
  • Cancer
  • Liver and kidney disease
  • Asphyxia

For more information consult the document Anesthetic Gases: Safe Use Guidelines.


What you can do to stay safe

  • Know what you are working with
  • Follow the procedures for safe handling and use of anesthetic gases and liquids
  • Ensure good ventilation and proper functioning and use of scavenging systems
  • Know signs and symptoms of expsoure
  • If unsure, ask for help
  • Contact EH&S if needed

Services available

EH&S provides the following services:

  • Consultation about exposure concerns to anesthetic gases
  • Anesthetic gas/vapor spill advice
  • Air monitoring for anesthetic gases


Call EH&S at 206.221.7770 to talk about exposure concerns to anesthetic gases.

Call EH&S for spill advice at 206.543.0467.

Call EH&S at 206.221.7770 for more information or to request air monitoring for anesthetic gases.


Environmental Health & Safety Department Contact

(206) 543-7262