IACUC Policy: Anesthesia Machine/Vaporizer/Waste Gas Maintenance and Certification    
Policy # IBT-202.00 IACUC Approval: February 27, 2014

Anesthetic vaporizers and gas anesthesia units are designed to deliver an accurate level of anesthetic vapor in a controlled and safe manner to animals to induce and reliably maintain an appropriate depth anesthesia with minimal exposure of personnel. The proper operation of these units is essential to minimize potential pain and suffering, to ensure the maintenance of reliable and safe anesthesia, and to minimize the potential of human health risks due to inadvertent exposure to anesthetic vapors.

This policy applies to all anesthetic vaporizers and gas anesthesia units that are for animal use subject to oversight by Texas A & M Health Science Center.

There is a difference between an on-site calibration and having the vaporizer sent to the manufacturer for preventive maintenance. The services performed in each of these instances can be significantly different. During most on-site calibrations, the vaporizer is checked to ensure it is delivering the amount of anesthetic as reflected by the setting. When vaporizers are sent in for preventive maintenance, the vaporizer is broken down and a detailed maintenance is performed that includes cleaning and replacement of worn gaskets and other parts. The frequency of these types of services depends on the type of vaporizer and anesthetic being used.   For example, a precision vaporizer using halothane requires more frequent calibration and maintenance due to the buildup of thymol (a preservative used in halothane) residues within the vaporizer.   Other volatile anesthetics, such as isoflurane and enflurane, do not contain thymol and do not require as an intensive calibration and maintenance schedule.

NIOSH (Health Care Workers Guidelines/Chap5) states that all anesthetic equipment must be regularly monitored for leakage, improper design, or defects. This includes the anesthesia machine as well as the vaporizer since anesthetic machines can develop improperly functioning components such as flutter valves, gaskets, and scavenging equipment.

Anesthetic machines and vaporizers are evaluated for safe and effective operation on an established schedule, consistent with the manufacturer’s recommendations.  The manufacturer of the vaporizer should have recommended intervals for both on-site calibration and for maintenance that requires sending the vaporizer in to them, as well as recommended maintenance intervals for the rest of the anesthetic machine.

It is the responsibility of all personnel who use anesthetic vaporizers and gas anesthesia units to be adequately trained in their use, maintenance and safety, and to adhere to these guidelines.
It is the responsibility of the Principal Investigator to make sure that all personnel on their AUP is adequately trained and is responsible for enforcing this policy with their staff.
It is the responsibility of the Program for Animal Resources to enforce this policy with their staff and to provide training to others when the need arises.

Anesthesia: Loss of sensation resulting from pharmacologic depression of nerve function or from neurogenic dysfunction. The American College of Veterinary Anesthesiologist define anesthesia as the application of methods to relieve pain, to relax muscles and to facilitate restraint during surgical, obstetrical and other medical procedures.

I. Anesthesia equipment must be maintained in good working order to assure personnel safety as well as precision delivery of anesthetic agents in an effective and predictable manner to patients.
Certification and calibration of vaporizers must be done by qualified personnel or an authorized service center and be performed according to manufacturer’s recommendations.

II. In the absence of manufacturer’s recommendations, certification must be performed at least once every year by qualified personnel or an authorized service center. Anesthetic machines and vaporizers must be tagged with the date of certification or expiration of certification, and made available to Safety and Institutional Animal Care and Use Committee personnel during laboratory inspections and IACUC semiannual inspections.

III. An effective mechanism of waste gas scavenging is essential, and required, as waste anesthetic gases may adversely affect liver, kidney and the central nervous system of chronically exposed personnel. This may be done by evacuation to house exhaust if air is not re-circulated, through the use of scavenging canisters, or use of an appropriately vented hood.

  1. Dedicated Exhaust: A dedicated exhaust or zone capture exhaust is preferred for removal of waste gases from the surgical theater or procedure space. These could include an active ‘vacuum’ waste gas line or an ‘elephant’ trunk exhaust.
  2. Fume Hoods: The use of a fume hood to capture the waste gas is acceptable. If an anesthesia machine is being used, then placement of the exhaust gas line inside of the fume hood is appropriate.
  3. Charcoal canisters: Charcoal canisters may be used to absorb halogenated waste gases. These canisters ARE NOT effective for capture of nitrous oxide The proper methodology of monitoring canister life involves logging the weighing of the canister or hours of use before or after each use and discarding the canister or hours of use in accord with the manufacturer’s instruction. .
  4. Soda lime/Baralyme (CO2 absorbers) should be change regularly, in accord with manufacturer’s instructions CO2 absorbers react with water; the pH change of becoming saturated with CO2 will activate a change in the ethylene violet dye indicator contained in these absorbers. These indicators can change back to white-grey if enough time is allowed, this however does not indicate the absorbers are still functional.

IV. Training is available through the PAR and is available to provide guidance and coordination by request.

V. Service may be provided by the manufacturer or a third party service provider such as:

  1. VetEquip, Inc. , P.O. Box 10785, Pleasanton, CA 94588-0785, 800-466-6463, Fax: 925-463-1943, info@vetequip.com
  2. Veterinary Anesthesia Systems Inc. Mr. Bill Quist at P.O. Box 10397, Phoenix, AZ 85064. 800.498-5575. http://www.vasinc.net
  3. JB Anesthesia Service. Mr. Jeff Barowitz at 523 Chasewood Dr., Grapevine, TX 76051. 817.437.3710. J.barowitz@verizon.net
  4. Handlebar Anesthesia Service. Mr. William Connery at 402A W. Palm Valley Blvd. Round Rock, TX. 78664. 512.670.2906. handlebaranesthesia@yahoo.com


  1. Guide for the Care and Use of Laboratory Animals, Institute of Laboratory Animal Resources, National Academy Press, Washington, D.C.
  2. Animal Welfare Regulations, Code of Federal Regulations, Title 9 - Animals and Animal Products, Chapter 1 – Animal and Plant Health Inspection Service, Subchapter A – Animal Welfare
  3. Occupational Health and Safety in the Care and Use of Research Animals, Institute of Laboratory Animal Resources, National Academy Press, Washington, D.C., 1997.
  4. Hazard Communication Standards, Code of Federal Regulations, Title 29, Part 1910.1200 - Occupational Safety and Health Standards, Subpart Z - Toxic and Hazardous Substances.
  5. Occupational Exposure to Hazardous Chemicals in Laboratories, Title 29, Part 1910.1450 - Occupational Safety and Health Standards, Subpart Z - Toxic and Hazardous Substances.
  6. Criteria for a recommended standard occupational exposure to waste anesthetic gases and vapors; DHEW Pub. No. (NIOSH) 77-140, March1977. www.cdc.gov/niosh/77-140.html
  7. Anesthesia. American College of Veterinary Anesthesiologist. www.ACVA.org

Original Version 00 -  February 27, 2014