Skip to Main Content




The National Institute for Occupational Safety and Health (NIOSH), while unable to define safe levels of exposure, recommends limiting trace gas levels to:

Table Graphic Jump Location

In most cases, the amount to anesthetic delivered exceeds the patient’s minimal requirement. Waste gas scavenging systems help to collect and remove excess anesthetic gases that would otherwise contaminate the operating theater. Scavenging is the process by which waste anesthetic gases flowing from the patient circuit are collected, controlled, and evacuated from the workplace, to reduce ambient concentrations of agents or gases. Active scavengers use a vacuum to remove waste gases. Passive scavengers rely on the physical properties of the gases for elimination.


Anesthetic gas contamination occurs via two causes: anesthetic technique and equipment issues. Technical issues include using flows that exceed the scavenging system, poorly fitting face masks and laryngeal mask airways, flushing the circuit, leaving the anesthetic gas on after a case, filling of vaporizers, using uncuffed endotracheal tubes, and use of independent breathing circuits (ie, Jackson Rees). Equipment failures include leaks, disconnections, and malfunctioning scavenging systems.


Scavengers can fail from an obstruction. Valves help a malfunctioning scavenger by protecting from excessive pressures. Open scavenging systems are without valves. Closed systems use either positive or positive and negative pressure relief valves.



++ ++

Components of a scavenging system. (Reproduced with permission from Barash PG, Clinical Anesthesia, 7th ed. Philadelphia, PA: Wolters Kluwer Health/Lippincott Williams & Wilkins; 2013.)

Graphic Jump Location

  1. The Gas Collecting Assembly receives waste gases from either the adjustable pressure-limiting valve or ventilator relief valve.

  2. Transfer Tubing carries the waste gases from the gas collecting assembly to the scavenging interface. The ASTM F1343-91 standard requires that the tubing be either 19 or 30 mm to distinguish it from the 22-mm breathing tubing. The tubing should be short and rigid to prevent kinking and occlusion, which can result in back pressure and ultimately barotrauma.

  3. The Scavenging Interface protects the circuit and ventilator from positive and negative excessive pressures. Open systems are without valves, and stay open to atmospheric pressure. They require an active disposal system. Closed systems use either positive pressure valves or both positive and negative pressure valves.

  4. Gas Disposal Tubing connects the scavenging interface to the gas disposal assembly. It should be robust as to prevent collapsing.

  5. The Disposal Assembly is either active or passive, and eliminates the gases to the atmosphere. Active systems use a vacuum to eliminate waste, whereas passive stems rely on the heavier weight of anesthetic gases to force waste ...

Want remote access to your institution's subscription?

Sign in to your MyAccess profile while you are actively authenticated on this site via your institution (you will be able to verify this by looking at the top right corner of the screen - if you see your institution's name, you are authenticated). Once logged in to your MyAccess profile, you will be able to access your institution's subscription for 90 days from any location. You must be logged in while authenticated at least once every 90 days to maintain this remote access.


About MyAccess

If your institution subscribes to this resource, and you don't have a MyAccess profile, please contact your library's reference desk for information on how to gain access to this resource from off-campus.

Subscription Options

AccessAnesthesiology Full Site: One-Year Subscription

Connect to the full suite of AccessAnesthesiology content and resources including procedural videos, interactive self-assessment, real-life cases, 20+ textbooks, and more

$995 USD
Buy Now

Pay Per View: Timed Access to all of AccessAnesthesiology

24 Hour Subscription $34.95

Buy Now

48 Hour Subscription $54.95

Buy Now

Pop-up div Successfully Displayed

This div only appears when the trigger link is hovered over. Otherwise it is hidden from view.