SAN DIEGO STATE UNIVERSITY
ENVIRONMENTAL HEALTH AND SAFETY DEPARTMENT
ANESTHETIC GAS USE AND SCAVENGING SYSTEM IN ANIMAL RESEARCH
POLICIES AND PROCEDURES
Introduction
Inhalant anesthetic gases (e.g. halothane, isoflurane, etc.) are increasingly employed in the research
setting for animal anesthesia and euthanasia. The anesthetic gases and vapors that leak into the
surrounding room during anesthetic administration process are considered waste anesthetic gases
(WAGs). Employees who work in this environment are potentially exposed to waste anesthetic gases
and are at risk of occupational illness. Exposure to anesthetic gases can result in toxicity to humans.
The waste anesthetic gases and vapors of concern are nitrous oxide and halogenated agents (vapors)
such as halothane, enflurane, isoflurane, desflurane, sevoflurane, and methoxyflurane. These gases
are typically clear, colorless, volatile liquids at ordinary temperature and pressure. These gases
possess very poor warning properties and therefore provide no indication (such as odor) that
exposure to these substances is occurring. 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.
Purpose
The Environmental Health and Safety (EHS) Department has developed this policy and procedure
document to protect employees at San Diego State University who have an occupational exposure to
anesthetic gases.
This document also provides general information on halogenated anesthetic gases and workplace
exposures. Exposure control measures to protect the health and safety of employees from
occupational exposure to isoflurane, a commonly used halogenated anesthetic gas in veterinary
practices or animal research are also identified and described.
Scope
This policy and procedure document applies to all San Diego State University (SDSU) employees
involved in veterinary care or animal surgical procedures where there is potential exposure to
halogenated anesthetic gas such as isoflurane. Nitrous oxide is not covered by this document because
it is typically used in animal research.
Policy
To reduce the risk of anesthetic gas exposure to personnel, proper maintenance of anesthesia
equipment, safe administration techniques, and appropriate waste scavenging systems must be
employed. Anesthesia machines, ventilators, and breathing systems must be checked annually and
maintained in good working condition to assure that they do not leak anesthetics into the atmosphere
of the workplace. Tubing, hoses, rubber items, and seals require periodic replacement.
Administration of inhalant anesthetics must be carried out with an annually certified vaporizer or in a
vented fume hood using a technique that prevents personnel from coming into direct contact with the
anesthetic. Certification requires inspection, functional testing, calibration, and cleaning of the
vaporizer. It is the responsibility of the owner of the equipment to contact an authorized service
vendor, pay for service, and to maintain service records and certification for all anesthesia equipment
owned. The owner is responsible for ensuring that personnel are trained in the proper use of
anesthetic machines and vaporizers prior to operation, and ensuring safe handling of the animals and
the anesthetic agent. Waste anesthetic gases must be scavenged and waste scavenging systems,
equipment, and supplies must be maintained and inspected routinely.
In compliance with all applicable codes and standards, engineering controls should be utilized to the
maximum extent feasible to maintain exposures below recommended exposure limits, followed by
other control methods including work practices, and administrative controls. When possible, active
scavenging through the building waste gas disposal system should be utilized. If gas anesthesia must
be conducted in an area that is not interfaced with this system, a passive scavenging system may be
utilized.
Standard
Presently, the Occupational Safety and Health Administration (OSHA) has not adapted a regulation
or standard regarding waste anesthetic gases (WAG's). The National Institute for Occupational Safety
and Health (NIOSH) and the American Conference of Governmental Industrial Hygienists (ACGIH)
both have established recommended maximum limits for personnel exposed to waste anesthetic
gases. The limit for halogenated anesthetics is 2 ppm over any 1 hour period. Exposure to waste
anesthetic gases in veterinary practices greatly exceeds these recommended limits when waste
anesthetic gases are not scavenged. Halogenated waste anesthetic gases can be scavenged effectively
by activated charcoal.
Health Effects
Overexposure to anesthetic gases can result in toxicity to humans. Some potential acute effects of
exposure to waste anesthetic gas are nausea, dizziness, headaches, fatigue, and irritability. More
serious potential long-term exposure in those with frequent workplace use of anesthetics include liver
and kidney disease, cancer, sterility, miscarriages, and birth defects in offspring. Although modern
agents such as isoflurane pose less of a risk of toxicity than some of the agents used historically, it is
still necessary to minimize human exposure when working with anesthetic gases. Employers and
employees should be aware of these potential health effects and be advised to take appropriate
precautions.
Pregnancy and Anesthetic Agents
Women of childbearing age should be aware that, although the risks are not completely understood,
exposure to anesthetic gases such as halothane and isoflurane may pose risks to a developing fetus
and therefore exposure during pregnancy is not recommended. For more information, contact EHS
at (619) 594-2865.
Definitions and Key Terms
OSHA: Occupational Safety and Health Administration.
NIOSH: National Institute of Occupational Safety and Health.
TWA: Time Weighted Average. The actual measured exposure level averaged over an eight-hour
time period.
Recommended Exposure Limit (REL): Exposure limits developed by the National Institute for
Occupational Safety and Health (NIOSH).
TLV: Threshold Limit Value Exposure limits published by the American Conference of
Governmental Industrial Hygienists (ACGIH).
WAG: Waste Anesthetic Gas
Responsibility
The EHS Department has the following responsibilities related to waste anesthetic gas activities:
1. Policy and Program Development, Implementation and Enforcement
2. Hazard and Risk Assessment
3. Area and Personal Air Monitoring to Determine Employee Exposure
4. Exposure Control and Reduction
5. Training
6. Medical Monitoring
Principal Investigators, Lab Managers, Veterinarians and OLAC Manager have the following
responsibilities related to waste anesthetic gas activities:
1. Assessment of their site and operations to determine whether isoflurane or other anesthetic
gases are present or used.
2. Review and approve proposed uses of isoflurane or other anesthetic gases within their areas in
order to comply with OSHA, EPA, and other government regulations. Such compliance includes
the following actions:
• Provide the resources necessary to control hazards.
• Ensure the availability and proper function of safety equipment, i.e., alarms,
detectors, ventilation equipment, and vacuum scavenging equipment.
• Maintain an adequate stock of required personal protective equipment (PPE).
• Provide equipment such as eyewash stations, and ventilation devices.
• Maintain anesthetic gas equipment.
• Make requests to the EHS department for required exposure monitoring and hazard
assessment of work activities.
• Maintain relevant Material Safety Data Sheets (MSDS) for anesthetic gases used.
• Provide employee training regarding the safe use, storage, and disposal of waste
anesthetic gas.
3. Limit or restrict expose to pregnant women to anesthetic gas, as it may cause adverse
reproductive effects.
4. Make available to all users a copy of this policy and procedure document. Additional copies
are available through the EHS department.
5. Ensuring all personnel have been trained prior to anesthetic gas use.
Anesthetic Gas Users are those workers have the following responsibilities:
1. Attend and complete required anesthetic gas safety training classes.
2. Properly use and maintain PPE.
3. Comply with SDSU policies, government regulations, and Standard Operating Procedures as
they pertain to anesthetic gas use.
4. Inspect all anesthetic delivery systems and connections for leak checks on anesthetic machines
used before starting anesthetic gas administration and after each use.
5. Eliminate or replace loose-fitting connections, loosely assembled or deformed slip joints and
threaded connections, and defective or worn seals, gaskets, breathing bags and hoses.
6. Ensuring the WAG scavenging system is used with all anesthetic gas machines.
7. Ensuring a WAG scavenge system (such as a chemical fumehood, a vacuum line out of the
building, a down draft table, or an exhaust ducted biosafety cabinet) is used when using bell jar
or any other anesthesia induction method that releases anesthetic gases into the procedure area.
8. Reporting problems with equipment with management, supervisors, or EHS.
9. Reporting chemical spills, releases, signs and symptoms, and any health and safety concerns to
management, supervisors or EHS.
Sources of Releases and Exposure
People working with volatile anesthetic gases can be exposed to waste anesthetic gases (WAG),
especially in the following situations when anesthetizing rodents:
 When using nose cone/face masks that does not form a tight seal around the animal’s face. WAG
can leak around the mask into the room.
 When using an induction chamber. Opening the charged chamber to retrieve the induced animal
releases WAG into the room. Sliding induction chambers are safer than hinged.
 When using an open system (bell jar, conical tube) rather than a vaporizer with scavenging
system.
Elevated levels beyond acceptable limits are an indication of faulty anesthesia equipment, equipment set
up, and/or improper anesthetic techniques.
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Faulty anesthesia equipment or equipment set-up – leakage from anesthesia equipment, improper
connections in the breathing circuit and/or scavenging system, defects in hoses, reservoir bags,
bellow, induction chamber seals, and Y-connector, improper use of gas scavenging system.
Improper anesthetic techniques – gas flow set too high, leaving flow valves and vaporizers on
after use, flushing the system into the room rather than the scavenging system, poor fitting of face
masks, leaving induction chambers open, and careless filling of vaporizers.
Engineering Controls
Scavenging systems coupled with an activated charcoal absorption system for halogenated hydrocarbons
collect, remove, and properly dispose of waste anesthetic gases away from buildings and are the primary
and preferred method for protection against exposure. 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. An effective room
HVAC system when used in combination with an anesthetic gas scavenging system should reduce,
although not entirely eliminate, the contaminating anesthetic gases. If excessive concentrations of
anesthetic gases are present, then airflow should be increased in the room to allow for more air
mixing and further dilution of the anesthetic gases. Supply register louvers located in the ceiling
should be designed to direct the fresh air toward the workers to provide dilution, and removal of the
contaminated air from the operatory. Exhaust register louvers should be properly located (usually
low on the wall near the floor level) in the room to provide adequate air distribution. They should
not be located near supply air vents because this will short-circuit the airflow and prevent proper air
mixing and flushing of the contaminants from the room
In order to reduce the risk of exposure to escaped vapors, one of the following engineering control
measures should be in place during the anesthetic application process:
First Choice: Placement of entire gas mixing and delivery system inside a fume hood.
Second Choice: Installation of local exhaust over single source anesthetic gas, or installation of slot or
canopy exhaust for procedures that involve multiple sources of anesthetic gas.
Third Choice: Capture of waste gas using gas scavenging canisters. This method is only recommended as
a control measure under the following circumstances:
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There is no fume hood or other local exhaust system available for use.
Leak checks are performed routinely on equipment.
Saturation levels of canisters are checked prior to each use.
Researchers are well trained and supervised in proper use and maintenance of the anesthetic
equipment.
Note on the use of gas scavenging systems:
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Absorption canisters with exhaust ports located on the top work better than those with the
exhaust ports on the bottom. Both types of cylinders should be used in the upright position;
however, the location of the exhaust ports on the top of the canister alleviates back pressure
and minimizes development of the open channels through the charcoal which results in better
capture.
Decreasing oxygen flow rates during anesthetic gas administration can also reduce the
concentration of waste gases in the work environment. For example, reducing the oxygen
flow rate from 2 to 0.4 lpm for a single mouse on a nose cone will still anesthetize the mouse
while reducing the concentration of waste gases in the work environment to more acceptable
levels.
Administrative Controls
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Follow Standard Operating Procedures (SOP) for the anesthetic machine, related equipment,
and scavenging system.
Evaluation of the scavenging system used and its maintenance as part of the APF review.
It is required that a trained technician perform the inspection, tests and maintenance of the
anesthetic machine at least annually or per manufacturer’s recommendations.
Documentation of validation must be affixed to each piece of equipment that is in service.
Use of animal anesthetics must be performed in an area with good ventilation and controls to
capture and exhaust waste anesthetic gases.
Work Practice Controls
Reduce exposure to waste anesthetic gases by: utilizing scavenging systems; leak-testing equipment;
properly fitting face masks; connecting tubes and fittings properly; using keyed filler systems or
bottle adapter with spout; filling vaporizers when few people are around; using low fresh-gas flow
rates; turning off the gas prior to removing animal 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.
Safety Consideration
The oxygen concentration delivered will be ~98% (room air is 20-21%), increasing the
combustibility of any material this oxygen-rich atmosphere contacts. Exercise care with any nearby
heat or ignition sources e.g. cauterizing device.
Hazard Communication
In accordance to OSHA’s Hazard Communication Program, a current Safety Data Sheet (SDS) for
anesthetics used must readily available. All containers such as canisters, tanks, and canisters shall be
labeled as to the identity of the contents, the manufacturer name, and the appropriate hazard
warnings.
Exposure Monitoring
EHS can perform air monitoring to determine anesthetic gas concentration in the work area. Two
types of monitoring can be performed: personal and area. Personal monitoring is conducted at the
employee’s breathing zone to determine WAG exposure for the employee. The monitoring is
performed using a standard size Anasorb Carbon Molecular Sieve (CMS) tube or ChemDisk Personal
Monitor and analyzed by a certified laboratory. Area monitoring is conducted in the work area to
determine WAG s in work areas. Comprehensive leak testing on the equipment to determine if gas is
escaping from various locations in the machine shall be performed by a qualified contractor.
Preventive maintenance should be performed by trained individuals according to the manufacturer’s
recommendations and at intervals determined by equipment history and frequency of use.
Monitoring environmental concentration of anesthetic gases determines effectiveness of the waste
gas control program and aids in identifying sources of leaks.
Monitoring/Reporting Results
EHS shall report the results of anesthetic gas monitoring to the person(s) monitored within fifteen
calendar days of the date on which the area supervisor receives the results. If the TLV has been
exceeded, the Principal Investigator or lab manager should refer to this document to review and
implement any of the applicable control measures which may help reduce the exposure to anesthetic
gases. The affected employees should be notified of any corrective action taken.
Medical Surveillance
Individuals working with anesthetic gas will complete an Occupational Health and Safety Risk
Assessment Form and indicate their potential exposure to halogenated anesthetics as part of Medical
Surveillance.
Training Program
All employees with any potential exposure to anesthetic gas must receive training to confirm their
understanding of anesthetic gases, its hazards, standard operating procedures, and methods of
protection. Employees should be trained at the time of initial assignment. The training program shall
be conducted in a manner in which the employee is able to understand and apply the following
information:
A. The properties, its forms, and uses
B. Recommended exposure limits
C. Routes of exposure and acute/chronic health effects
D. Description of signs and symptoms of potential exposure
E. Control measures employees must take to protect themselves
F. WAG scavenge systems and anesthetic gas equipment inspections
F. Emergency procedures for spills/release and exposures
Emergency Spill/Release Response
Spills of liquid anesthetic agents evaporate quickly at room temperature. Laboratory personnel may
perform the clean-up of small spills (25 ml or less) provided that the laboratory personnel have
access to appropriate personnel protective equipment as directed by the Safety Data Sheet (SDS) and
the agent can be absorb with paper toweling at the time of the release. If absorbed, the waste
material shall be placed into a sealed container, labeled and referred to EHS for final disposal.
In the event the spill involves more than an estimated 25 ml, laboratory personnel are to vacate the
room immediately and are to secure the room from general access by closing all doors leading to the
spill area. The spill is to be reported to EHS x46778. Campus spill response representatives will
respond to the scene to further evaluate the release and determine when the area is safe for re-entry.
Emergency Exposure Procedure
Eye Care: If anesthetic gases come in contact with eyes, immediately flush them with copious
amounts of water for at least 15 minutes, preferably in an emergency eyewash.
Skin Care: In the event of skin exposure, remove contaminated clothing and immediately wash the
affected area with soap and water.
If Swallowed or Inhaled: In the case of ingestion, obtain medical attention immediately. If anesthetic
gases are inhaled, move the victim to a source of fresh air.
Note: After any over exposure to anesthetic gases via skin, inhalation, ingestion, or eye contact, the
victim should immediately seek medical evaluation. Employee will immediately report any work
related exposure, injury or illness to his/her supervisor and EHS.
Waste Disposal
Containers of expired or unused liquid anesthetic agents and spent waste anesthetic gas canisters are
to be disposed through EHS Hazardous Waste Program by contacting x46778 for proper disposal.
Record Keeping
Maintenance logs of inspection, service, testing, and caibration should be kept for each anesthetic
machine, vaporizer, and ventilator. Information that must be maintained includes:
 Date of last service and calibration
 Initials of the person who performed the service and calibration
 Service and calibration results
Documentation of service and calibration must be affixed to each anesthesia machine or vaporizer
that is available for use.