Anesthetic gases are commonly used throughout the University. Anesthetic gas and vapors that leak into the surrounding room during medical or research procedures are considered waste anesthetic gases (WAGs.) Individuals working with these anesthetic gases must be aware of the potential hazards associated with them, and must be trained and proficient in methods to work with the gases in a safe manner.
Workers acutely exposed to excess amounts of anesthetic gas can experience symptoms of drowsiness, headaches, nausea, poor judgment and loss of coordination. Chronic symptoms of over-exposure can include liver, kidney and reproductive effects.
This document will provide guidance to all researchers and employees who use anesthetic gases.
Sources of Exposure
Poor anesthesia techniques, improper practices or faulty equipment can contribute to the escape of WAGs into the environment. The following are common examples:
- Bench top delivery of inhalant anesthetic without adequate scavenging.
- Poorly fitted face masks.
- Use of un-cuffed ET tubes or improper inflation of cuffs on ET tubes
- Turning on flow meters or inhalants before attaching breathing system
- Disconnecting subjects from the anesthesia machine before WAGs have been adequately scavenged.
- Leaks in the anesthetic delivery system
Presently the Occupational Safety and Health Administration (OSHA) have not created a regulation regarding WAGs. However, national recognized organizations such as The National Institute for Occupational Safety and Health (NIOSH) and the American Conference of Governmental Industrial Hygienist (ACGIH) have both recommended exposure limits for WAGs. Environmental Health & Radiation Safety (EHRS) may be consulted for guidance on any gas that is not listed in the table below.
(see note 1)
(see note 2)
(see note 3)
Nitrous Oxide (N2O)
(see note 4)
(see note 5)
(see note 5)
(see note 5)
(see note 5)
(see note 5)
(see note 5)
1-PEL:permissible exposure limit, ppm: parts per million
2-REL: recommended exposure limit measured as a time weighted average (TWA) during the period of anesthetic gas administration, not to exceed one hour.
3-TLV-TWA: threshold limit value-time weighted average. This value refers to an 8-hour workday and a 40-hour work week.
4-Measured as a TWA over the period of anesthetic gas administration.
5-Ceiling limit concentration of no greater than 2 ppm over a period not to exceed one hour.
The Principal Investigator (PI) is responsible for training their staff prior to beginning any work which involves anesthetic gases. The training shall include the following: applicable regulatory limits, health effects of anesthetic gases, sources of exposure, WAG scavenging systems, anesthetic gas equipment and inspections, risk assessments, personal protective equipment, Safety Data Sheets (SDS), standard operating procedures, engineering controls, work practices, administrative controls, chemical spills, air monitoring and hazard communication. The training shall be conducted upon initial assignment and whenever there is a change in the process or procedure. All training must be documented and be readily available for review.
Controlling Anesthetic Gas Exposure
It is imperative that the Principal Investigator (PI) conducts a thorough risk assessment and prepares protocols which include standard operating procedures (SOP), identifying appropriate administrative controls, personal protective equipment (PPE), work practices and engineering controls for eliminating or sufficiently reducing exposure to all potential affected individuals. Refer to OSHAs Anesthetic Gases: Guidelines for Workplace Exposure document for further information on how to reduce workplace exposure to WAGs.
The following engineering controls are recommended when working with Anesthetic Gases:
- A reliable and appropriate Waste Gas Scavenging System or other approved local exhaust ventilation system to collect, remove and dispose of WAGs. Scavenging options include:
- Dedicated exhaust systems: A dedicated exhaust system such as an active vacuum waste gas line or an “elephant trunk” exhaust system is the preferred method to remove waste gases from the work environment.
- Non-circulation ventilation systems: These discharge waste gases through an exhaust vent or grill( ex. Hard ducted biosafety cabinet( Class II, Type B2) or downdraft table)
- Chemical fume hood: The anesthetic can be delivered to the animal while it is inside the fume hood or an exhaust gas line from the anesthesia machine can be vented inside the hood.
- Adsorption devices: Charcoal canisters such as F-Air or Enviro-Pure can be used to absorb halogenated waste gases. These canisters must be properly placed so that the vent holes on the bottom of the canister are not obstructed. Usage must be documented and accompanied by the method used to determine canister life as supplied by the manufacturer. For F-Air canisters this involves weighing the canister before and after each use, recording the weights on the device (or in a readily available log) and discarding when there is a 50 g increase from the initial weight. Adsorption devices are not be used for N2O.
- Anesthetic Gases shall be used in a well ventilated area such as a laboratory or operating room. It is recommended that the HVAC system be capable of providing at a minimum of 10 air changes per hour (ACH) of uncirculated air.
The following administrative controls are recommended when working with Anesthetic Gases:
- Standard Operating Procedures (SOP) - All areas that work with anesthetic gases shall develop a SOP specific to the anesthesia apparatus and gas used in the area. The SOPs need to be reviewed and/or updated at least annually or whenever there is a change in operations or gas used or stored.
- Preventive Maintenance Program for Anesthesia Apparatus/Equipment- The program shall include the following:
- Comprehensive Leak Testing
- Adjusting all components of the machine
- Any required calibration
A trained technician shall perform these tests at least annually. The manufacturer’s manual shall be consulted to determine if there are any other requirements. All documentation shall be readily available for review.
- Purchase & Storage Requirements
- Buy the least amount of products used for anesthesia as possible. Do not buy large quantities.
- Label all containers with the following information:
- Name of the material
- Warnings/Hazard Information
Personal Protective Equipment (PPE)
The following are recommended:
- The PI shall conduct a risk assessment based the Safety Data Sheets (SDS), manufacturer’s manual or other safety references to determine the type of PPE that is required.
- The following minimum PPE shall be required:
- Safety Glasses or face shield
- Appropriate gloves
- Lab Coats, aprons or other suitable clothing
- Closed toe shoes
The following work practices are recommended when working with Anesthetic Gases:
- Work in a well-ventilated room with at least 10 air changes per hour (ACH)
- Use the least hazardous product and delivery system available for the task.
- Check anesthesia machines, breathing systems, and scavenging systems for leaks before each use.
- Procedures or techniques that have a potential for exposure shall be conducted in a certified chemical fumehood, hard ducted Biological Safety Cabinet, downdraft table, or other local exhaust system that allows the rapid elimination of WAGS from the work place. Examples include but are not limited to:
- Pouring of Liquid Anesthesia
- Filling of the Vaporizer
- Open drop (periodically dripping liquid volatile anesthetic onto a gauze sponge)
Restrict access to the work area
- Turn on flow meters and vaporizers only when needed and turn them off when finished.
- Use the lowest flow of fresh gas as is safely possible for the subject and the machine.
Exposure monitoring shall be conducted as necessary to assure that safe levels are being maintained. Two types of monitoring shall be performed, personal and area. Personal monitoring is conducted at the employees breathing zone to determine WAGs exposure for the employee. Area monitoring is conducted in the work area to determine WAG concentration in work areas. All results shall be reviewed with monitored individuals. All records must be readily available for review.
EHRS can conduct exposure monitoring when requested by the PI. All cost associated with the monitoring will be the responsibility of the requestor. Refer to EHRS policy 5-16-Monitoring for Hazardous Chemicals for additional information.
Any individual who was potentially over-exposed or is experiencing symptoms should immediately seek medical consultation. Please EHRS policy 1.8-Medical Assessment and Treatment for additional information.
The EHRS Waste Management section can be reviewed for information on how to properly identify and dispose of Hazardous Waste.