Halogenated Anesthetic Gas (Isoflurane Gas Use)

 

A laboratory professional carefully handles a vial in a sterile environment, showcasing precision in research.

Overview
Regulatory & Exposure Guidance
Health effects of Exposure
Routes of Exposure
Waste Anesthetic Gas (WAG) Controls
Recommended PPE
Equipment & Safe Work Practices
Vaporization Guide
Institutional Animal Care and Use Committee (IACUC)
Waste Disposal & Spills
Medical Surveillance & Training

 

Overview

Isoflurane is a halogenated inhalation anesthetic widely used in laboratory animal research.  It is typically administered at concentrations of 0.5%–3% in oxygen using precision vaporizers. It is a clear, colorless, nonflammable, volatile liquid at room temperature and pressure. It has an odor that has been described as ether-like or sweet. Isoflurane is structurally and pharmacologically similar to other halogenated anesthetics,  including halothane desflurane, enflurane, sevoflurane. For summarized information on halogenated anesthetic gases, please refer to fact sheet below.

Fact Sheet

Due to isoflurane’s volatility at room temperature, improper handling, inadequate ventilation, and/or lack of adequate engineering control can result in occupational exposure. Consequently, safe work practices, engineering controls, and proper scavenging systems must be used to minimize exposure.

 

All groups working with isoflurane or other anesthetic gases must have the following:

 

Please contact EHS at env-health-occ-health@ncsu.edu for additional assistance.

 

Regulatory & Exposure Guidance

There is currently no OSHA Permissible Exposure Limit (PEL) established specifically for isoflurane. However, OSHA does reference exposure guidelines provided by the following organizations:

  • National Institute for Occupational Safety and Health (NIOSH)
    • Recommends a ceiling concentration of 2 ppm for any halogenated anesthetic gas during a sampling period not exceeding 1 hour.
  • American Conference of Governmental Industrial Hygienists (ACGIH)
    • No specific TLV for isoflurane.
    • Recommends maintaining exposure below 50 ppm, based on comparisons to halothane.

 

EHS recommends maintaining exposures as low as reasonably achievable (ALARA) through engineering controls and safe work practices.

 

Health Effects of Exposure

Some health effects of isoflurane are summarized in the table below

 

Acute (Short-Term) Effects

Chronic (Long-Term)

And Reproductive Concerns
Headache Increased risk of miscarriage
Drowsiness Reproductive effects
Nausea Genetic damage
Eye, skin, and respiratory tract  Birth defects
Irritation Liver and kidney disease
Dizziness
Potential effect on liver or kidney function with high exposures

 

Minimizing occupational exposure is critical, especially for individuals who are pregnant or planning pregnancy.

 

Routes of Exposure

Workers are primarily exposed through inhalation of waste anesthetic gas (WAG).

Common exposure points include:

  • Open drop method (bell jar placement/removal)
  • Induction chamber opening
  • Nose cone placement and removal
  • Leaking tubing or fittings
  • Non-rebreathing circuit failures
  • Inadequate scavenging systems

 

Exposure risk increases when:

  • Equipment is poorly maintained
  • Scavenging systems are improperly installed
  • Recirculating biosafety cabinets (Class II Type A) are used instead of Type B2 cabinets with 100% total exhaust systems
  • Procedures are not followed as approved

 

NOTE: If isoflurane is splashed on skin or eyes, flush with plenty of water for at least 15 minutes.

If you plan to use isoflurane please contact EHS for an evaluation and potential exposure monitoring. 

 

Waste Anesthetic Gas (WAG) Controls

Managing WAG exposure follows a hierarchy of controls.

BEST: Engineering Controls (Ducted Systems

Certified Chemical Fume Hood or Class II Type B2 BSC
  • Perform procedures inside a certified chemical fume hood or hard-ducted BSC.
  • Exhaust must be ducted directly outside the building.
  • Verify certification has been completed within the past year

Do NOT use:

  • Recirculating (ductless) biosafety cabinets
  • Laminar flow hoods

These systems return vapors to the room and do not protect against WAG exposure.

 

GOOD: Active Scavenging 

Air cleaning extraction systems equipped with activated charcoal adsorption units may be used when ducted ventilation is unavailable.

  • Follow manufacturer specifications.
  • Do NOT connect to house vacuum lines unless evaluated and approved by EHS.

 

SUFFICIENT: Passive Scavenging

Charcoal Canisters
  • Relies on positive pressure from the anesthesia machine and animal exhalation.
  • Must remain upright and positioned below the vaporizer.
  • Ensure bottom airflow holes are not blocked.
  • Weigh before initial and every subsequent use, and record weight directly on canister
  • Replace when the weight increases by 50 grams or per the manufacturer’s maximum loading capacity.
Safety Notes
  • Charcoal adsorption units cannot be used with nitrous oxide (N₂O). Charcoal does not trap N₂O and provides no protection.

 

Equipment Calibration and Maintenance

  • Contact the equipment supplier or authorized technician regarding
    • Proper handling of isoflurane equipment
    • Annual calibration
      • Annual calibration for vaporizers is required unless the manufacturer states that calibration is not required
    • Maintenance
    • Leak/pressure testing of an anesthetic machine.

 

A researcher wearing protective gear takes a sample of a liquid in a laboratory.

 

Use the following personal protective equipment (PPE) to reduce the risk of exposure when handling isoflurane:

  • Nitrile gloves (double glove when filling vaporizers)
    • Change gloves immediately if contaminated
  • Lab coat or gown
  • Eye protection during filling or spill response
  • Avoid direct skin contact

 

Equipment & Safe Work Practices

Anesthesia Machine

  • Wear gloves, lab coat, and eye protection
  • Verify fume hood or vaporizer certification.
  • Fill/refill vaporizers utilizing best practices to minimize exposure and prevent leaks when refilling anesthetic vaporizers:
    • Perform refilling in a fume hood or ducted enclosure
    • Use keyed filling systems when possible
    • Keep bottles tightly closed
    • Avoid overfilling
    • Wipe the exterior of the bottle before storage
  • Perform leak test:
    • Reference the owner’s manual or manufacturer recommendations for a step-by-step guide

 

Induction Chamber

  • Use chambers with tight-fitting covers.
  • Hinged lids: open with hinge facing operator.
  • Sliding lids: slide perpendicular to operator.
  • Purge with oxygen ~10 seconds before opening.

 

Surgical Procedures

  • Use the best-fitting nose cone to minimize leakage.
  • Monitor induction and maintenance percentage of isoflurane 
  • Keep your breathing zone away from the mask/cone.
  • Shutdown sequence:
    • 1. Turn off isoflurane.
    • 2. Continue oxygen flow.
    • 3. Allow the animal to breathe oxygen for several minutes.

Administration of isoflurane in large animals must follow appropriate pre-medication and induction protocols

 

Open Drop Method

The open drop method should be avoided when possible. All open drop methods must also be approved by EHS before use. Please email env-health-occ-health@ncsu.edu to request an assessment. 

If required:

  • Perform inside a certified chemical fume hood.
  • Use the lowest effective concentration.
  • Preference given to 1000 mL chamber over 500 mL.
  • Limit procedure to <1 minute.
  • Use a tight-fitting lid.
  • Keep the lid closed except during animal placement/removal.
  • Do not use standard non-ducted biosafety cabinets or laminar flow hoods.

 

Vaporization Guide (for Small Animals Only)

Preferred: Diluted Gas Anesthesia

Diluted gas anesthesia minimizes lethal vapor accumulation and improves safety margins.

Recommended mixtures:

  • Mice: 20% v/v liquid anesthetic in propylene glycol
  • Rats: 30% v/v liquid anesthetic in propylene glycol

General guideline: ~1.0 cc diluted mixture per 500 cc chamber volume.

 

Undiluted Gas Anesthesia

Use precise measurements to prevent overexposure.

mL per Liter Approximate % Vaporization
0.05 1%
0.10 2%
0.15 3%
0.20 4%

Example Calculations

Example 1
10 cm × 10 cm × 10 cm chamber = 1000 cc or 1.0 L
For 1% vaporization → 0.05 mL liquid anesthetic

Example 2
8 cm × 10 cm × 7 cm chamber = 0.560 L
For 1% vaporization → 0.028 mL liquid anesthetic

 

Institutional Animal Care and Use Committee (IACUC)

Workers and supervisors with animal contact are subject ethical, practice, and care standards governed by federal and local laws, regulations and standards. Contact IACUC to ensure compliance with the university’s rigorous program of animal care and use.

 

Waste Disposal & Spills

Unused Isoflurane

Dispose through EHS Hazardous Waste Program via EHSA.
Email: env-health-haz-waste@ncsu.edu
Phone: 919-515-6859

Spills

  • Small Spills (<25ml): Small volume of anesthetic agents (isoflurane) evaporates so quickly at room temperature, and may dissipate before any attempts to clean up. For small spills (25ml or less), lab personnel may perform cleanup if trained and knowledgeable on how to do so. Appropriate personal protective equipment should be used as listed in the safety data sheet.
  • Large Spills (>25ml): Evacuate immediately. Contact University Police at 919-515-3000 or 911.

 

Medical Surveillance & Training

EHS will review incoming SOPs and all requests regarding potential exposure to evaluate the adequacy of controls (engineering and/or administrative controls) or the necessity to wear respiratory protection. If that is the case, personnel with routine exposure to isoflurane may be enrolled in Occupational Health surveillance as required by EHS.

Note: N95 and surgical masks will not offer any protection to personnel exposed to anesthetic gas

Training requirements may include:

  • Laboratory safety training
  • Anesthesia equipment training/WAG control procedures
  • SDS Review
  • Other site or job-specific training as required for the protocol

 

 

Questions?

Environmental Health & Safety
Email: env-health-occ-health@ncsu.edu
Phone: 919-513-0988

For questions regarding isoflurane use, waste anesthetic gas control, or occupational exposure monitoring, contact EHS Occupational Health.

 

Resources