Waste Anesthetic Gas’ Impacts on the Environment

How your lab can dramatically improve its carbon footprint

TL;DR

In this article, we dig into waste anesthetic gas’ impact on the environment. If you run mouse anesthesia at 1–1.5 L/min, most of what you deliver isn’t being used by the animal. It’s going to scavenging—or the room. Low-flow reduces the volume of anesthetic moving through the system. In the factsheet example, lowering flow from 1.5 L/min to 0.1 L/min holds the same 2% isoflurane concentration while cutting waste anesthetic gas volume dramatically.

The simple problem: the animal can’t “use” what you’re delivering

Most labs don’t set out to waste anesthetic gas. It happens because the anesthesia station is built around habits that were never designed for mice.

Factsheet Excerpt: the low-flow numbers most labs don’t have 

To understand the context of this article, we’re including this summary of a white paper on low-flow rodent anesthesia, where we walk through a simple mismatch that drives most waste anesthetic gas: traditional mouse inhalation anesthesia is often delivered at 1–1.5 L/min, while mice breathe an average tidal volume around ~26 mL/min, making the “minimum delivery rate” example ~52 mL/min. The majority of delivered anesthetic is therefore wasted into scavenging systems or the surrounding environment. 

Using representative mouse anesthesia settings, we compared the same 2% isoflurane concentration delivered at 0.1 L/min versus 1.5 L/min (a 15× flow reduction). The key point: the intended anesthetic concentration is held constant; the flow rate is what changes the waste volume. 

Since isoflurane has a global warming potential (GWP) 525x higher than CO₂, and sevofluorane has a GWP 130x higher than CO₂, that drives measurable downstream differences in the representative model: for isofluorane, the CO₂-equivalent emissions per hour (CO₂e/hr) are reduced from 7.2 kg to 0.5kg, plus major consumable efficiency changes—one bottle of isoflurane lasting 412 hours vs 27 hours, and a 10L oxygen tank lasting 908 hours vs 22 hours in the example. 

The same example pricing model (region-dependent) estimates a 29× reduction in running costs under representative European pricing, and shows how savings scale with usage.

Request the full low-flow factsheet white paper
Want the full set of assumptions, tables, and usage scenarios? Request access to the complete factsheet.

You see, when flow is that much higher than the animal’s ventilation, the difference doesn’t disappear. It becomes waste anesthetic gas—captured in scavenging, or escaping through leaks, open induction, and bad habits.

That’s why this topic matters to:

• lab safety (less WAG in the room)
• budget (less agent and carrier gas)
• environment (volatile agents have meaningful climate impact)

Why labs are thinking about the environment now

A lot of labs haven’t looked at waste anesthetic gas’ impact on the environment because they simply weren’t aware that it was a thing in years gone by.  

That’s simply not the case—particularly in European labs. 

Sustainability reporting is becoming normal in universities, hospitals, and multinational research programs.

Volatile anesthetics are greenhouse gases. The factsheet lists GWP relative to CO₂ as 130× for sevoflurane and 525× for isoflurane. Whether your facility tracks CO₂e today or not, those are the kinds of numbers procurement teams and sustainability offices now ask about.

The point here isn’t guilt—and sustainability. It’s control. Most labs can reduce waste without changing the science.

The three levers labs can control (and which one matters most)

1) Maintenance flow rate

This is the big one.

The factsheet makes a clean comparison: keep anesthetic concentration the same (2% isoflurane) and change flow.

• Traditional example: 1.5 L/min
• Low-flow example: 0.1 L/min
  That’s a 15× reduction in flow.

Same concentration. Less volume. Less waste.

The factsheet even translates that into CO₂e per hour in the example setup: 0.5 kg CO₂e/hr vs 7.2 kg CO₂e/hr. The exact conversion for your facility may be different,, but the direction is not controversial: high flow multiplies waste.

2) Carrier gas habits

Carrier gas is often set once and forgotten.

The factsheet’s representative comparison uses:

• room air supplemented with oxygen to 50% O₂ in the low-flow case
• 100% oxygen in the traditional case

This isn’t a “one right answer” issue. It’s an “are we doing this intentionally?” issue. If oxygen strategy impacts physiology or endpoints for your model, write it into the protocol and run it consistently.

Also: if nitrous oxide is part of your world, treat it variable, not a footnote. The factsheet notes that although N₂O has a lower GWP than isoflurane, it can dominate environmental impact when used at common mixes and higher flows.

3) Scavenging + leak discipline

Lower flow reduces the amount of anesthetic moving through the system. Scavenging and leak checks determine where the remainder goes.

If you want a station that’s easy to defend, don’t rely on memory:

• confirm scavenging is connected and functional
• do quick leak checks on a schedule
• standardize induction transitions

Small leaks are a smaller problem when you aren’t pushing high flow through the circuit.

A realistic way to estimate impact

Your facility’s exact CO₂e will vary by:

• your flow settings
• how many hours/week you run
• how many stations you have
• your agents and carrier gas choices

That’s why the factsheet frames impact by weekly hours.

Example savings per vaporizer in their model:

• 4 hrs/week: 1,353 kg CO₂e/year saved
• 10 hrs/week: 3,382 kg CO₂e/year saved

Treat those as “order of magnitude” anchors tied to the example assumptions, not as a universal promise. The useful thing is the method: hours × flow × agent.

What to standardize so this doesn’t depend on you alone

If you want this to stick, build it into the workflow:

• Define a maintenance flow range for mice vs rats
• Define when and why oxygen strategy changes
• Standardize induction transitions and scavenging checks
• Record the minimum: flow, agent %, duration, scavenging status

This is refinement in a very practical form. Less drift. Less waste. Better recoveries.

Where Kent fits

The low-flow example in the factsheet is framed around SomnoFlo® O2 Care, operating at 0.1 L/min in the representative comparison while maintaining 2% isoflurane concentration.

If your goal is to reduce waste anesthetic gas burden and bring oxygen strategy under SOP control, that’s exactly the problem this part of the SomnoFlo® line is designed to solve.

Practical next step: If you share:

• mouse vs rat
• hours/week under anesthesia
• typical maintenance flows
• number of stations

…we can help you estimate where the biggest controllable wins are likely to be—for safety, cost, and environmental reporting.

Waste Anesthetic Gas’ Impact on the Environment FAQ

What is waste anesthetic gas (WAG)?
WAG is anesthetic that isn’t taken up by the animal and ends up in scavenging or the surrounding environment. High delivery flows relative to animal tidal volume are a major driver.

What’s the best thing a lab can control to reduce WAG?
Use a lower maintenance flow rate. In the factsheet example, holding 2% isoflurane constant and reducing flow from 1.5 L/min to 0.1 L/min cuts the waste gas volume moving through the system.

Do volatile anesthetics affect climate impact?
Yes. The factsheet lists GWP relative to CO₂ as 130× for sevoflurane and 525× for isoflurane.

Is scavenging still necessary with low-flow?
Yes. Low-flow reduces the volume of waste gas, but scavenging and leak discipline still determine where it goes.