Desflurane and nitrous oxide:
the carbon footprint of anaesthetic gases in hospital

Since 1 January 2026, the EU F-gas Regulation has prohibited desflurane as an inhalation anaesthetic, except where no other anaesthetic can be used for medical reasons. According to the 2022 guidelines of the French Society of Anaesthesia and Intensive Care Medicine (SFAR), one hour of anaesthesia with desflurane is equivalent to 300 km by car, against 6.5 km with sevoflurane. The calculation assumes a car emitting 200 g of CO2e per km and rests on the warming potentials that SFAR uses.

Nitrous oxide falls outside the regulation because it contains no fluorine. Kilo for kilo, it nonetheless warms the climate more than sevoflurane, and a large share is lost in hospital pipework before it reaches the patient. For a hospital's management, the question becomes one of accounting: how much do these gases weigh in the hospital's emissions report, and how should they be counted from one year to the next?

1Why do anaesthetic gases weigh so heavily on the climate?

An anaesthetic gas is barely transformed in the body. According to SFAR, the body metabolises 5% of sevoflurane and 0.05% of desflurane: the rest is exhaled unchanged, then vented outside by the theatre's scavenging system. The health-sector guide published by ADEME (the French Agency for Ecological Transition) makes the same assumption for CO2 and N2O: 100% of the gas purchased is counted as released into the air.

The weight of this released gas is measured by its global warming potential (GWP), which compares the effect of one kilo of a gas with that of one kilo of CO2, over 100 years by convention. This article uses the values of the Sixth Assessment Report of the IPCC (Intergovernmental Panel on Climate Change), published in 2021, the most recent, which the EU regulation also adopts. Others are still in circulation: those of the Fifth Assessment Report (2013), 265 for nitrous oxide, and those of a 2012 study, 2,540 for desflurane.

Halogenated agents

Desflurane, sevoflurane and isoflurane are halogenated agents, fluorinated ethers vaporised into the air the patient breathes. Their effect depends on their GWP and on their lifetime in the atmosphere: 14.1 years for desflurane, 1.9 years for sevoflurane, according to the IPCC. Worldwide, SFAR cites an estimate of 3.1 million tCO2e in 2014 for halogenated agents released, 80% of it from desflurane.

The choice of agent accounts for most of the gap between 2 hospitals. A study published in 2017 in The Lancet Planetary Health, covering 3 hospitals in Canada, the United States and the United Kingdom, found a ratio of 1 to 10 in their anaesthetic gas emissions. The difference came from a preference for desflurane. SFAR makes the same observation for an operating theatre: its halogenated agent emissions are divided by 10 when desflurane is removed from the formulary.

Nitrous oxide

Nitrous oxide, or N2O, warms 273 times more than CO2 and stays in the air for 109 years. Its GWP is therefore the same over 20 and over 100 years, whereas that of halogenated agents falls as the time horizon lengthens. Used as a carrier gas with oxygen, it also multiplies by 6 the CO2 equivalent of a sevoflurane anaesthetic, according to the work cited by SFAR.

2How should a hospital count anaesthetic gases in its carbon footprint?

This is the question on which published figures diverge most. Depending on the method, the same bottle of desflurane counts as zero or close to a tonne of CO2e, and the published shares of this item range from 15% to less than 1% of a hospital's footprint. A Bilan Carbone® (the French carbon accounting method) measures only what its boundary includes, and anaesthetic gases are a textbook case.

How much the item weighs

The 2019 ADEME sector guide states that anaesthetic gases may account for up to 15% of a hospital's emissions, a figure it takes from a 2018 document produced by an association. At AP-HP, the Paris public hospital system, the medical gases category amounts to 16,040 tCO2e in the 2024 assessment, or 0.83% of the total of 1,935,943 tCO2e, by our calculation.

The 2 figures do not measure the same thing. The 15% predates the decline of desflurane. The 0.83% combines anaesthetic gases with the oxygen and nitrous oxide mixture, CO2 and medical nitrogen, without breaking them down, and the category fell by a further 20% in 2025. Above all, the counting method changes from one document to another.

The official French rule

The regulatory emissions report, BEGES (bilan d'émissions de gaz à effet de serre), France's mandatory greenhouse gas emissions report, counts the gases set by the ministerial order of 25 January 2016: CO2, methane, N2O, HFCs, PFCs, SF6 and NF3, the 7 gases also covered by the GHG Protocol. N2O is on the list. Halogenated agents, on the other hand, are fluorinated ethers, not HFCs in the strict sense: they do not literally appear on the list. The 2019 ADEME sector guide draws a strict rule from this. It counts CO2 and N2O only, as direct fugitive emissions. It flags halogenated agents as potent greenhouse gases, without counting them.

The French regulatory method also requires 100-year GWPs updated on the basis of the latest IPCC data. When it was published, in 2022, it referred to the Fifth Assessment Report, of 2013, which gives 265 for N2O and 1,790 for desflurane. With these GWPs, a 240 mL bottle of desflurane weighs 629 kgCO2e, against 911 with the 2021 values. ADEME's Base Empreinte, the French public emission factor database, now offers both sets, 265 and 273 for N2O. This article uses the Sixth Assessment Report, the most recent, which the EU regulation also adopts.

How AP-HP in Paris counts them

AP-HP does the opposite: it counts halogenated agents, but under its purchases of goods, category 4.1 of the BEGES, the one that covers scope 3. It starts from the volumes ordered in its management software and applies British per-bottle factors, published in an appendix to its assessment. A 240 mL bottle of desflurane counts there as 893.06 kgCO2e, a 250 mL bottle of sevoflurane as 49.47 kgCO2e.

AP-HP, 2024 GHG assessment

The per-bottle factors of a major French university hospital

AP-HP, Bilan des émissions de gaz à effet de serre 2024 (greenhouse gas emissions assessment), Appendix 2, Emission factors used, p. 77. Cited document, in French.

Appendix 2 of the AP-HP assessment gives 893.06 kgCO2e per bottle of desflurane, 76.30 for isoflurane and 49.47 for sevoflurane, with 30% uncertainty, based on the NHS. Nitrous oxide is counted at 265.43 kgCO2e per kilo, based on the French Base Carbone.

These factors can be reproduced by calculation. A 240 mL bottle of desflurane contains 351.6 g of gas, at the density of 1.465 given in the manufacturer's package insert. Multiplied by 2,540, these 351.6 g give exactly 893.06 kg. The NHS factors therefore rest on the GWPs published in 2012 by an atmospheric chemistry study, 2,540, 510 and 130, which SFAR also cites. They are neither those of the IPCC Fifth Assessment Report nor those of the Sixth. The AP-HP factor for N2O, 265.43 kgCO2e per kilo, comes from the French Base Carbone database and follows the Fifth Assessment Report.

The GWP set also changes the comparisons. With the 2021 IPCC values, the sevoflurane bottle weighs 74 kgCO2e, or 50% more than in the NHS factor, and 10% less than with the 2013 values. The figure of 18 times more emissions for desflurane than for sevoflurane, cited by AP-HP, is the ratio of the 2 NHS factors. With the 2021 GWPs, a bottle of desflurane weighs 12 times as much as a bottle of sevoflurane. Per hour of anaesthesia, the gap is much wider, because desflurane is administered at a higher concentration. It reaches 46 times according to SFAR, with the 2012 GWPs, and about 30 times with the 2021 values, by our calculation on the same assumptions.

Counting in kilos

There is therefore no single rule applied by everyone. A hospital may adopt a simple method and, above all, keep it from one year to the next, so that 2 successive assessments can be compared. It takes 4 steps:

• Record the quantities purchased during the year from the pharmacy, in bottles per product reference and in kilos of N2O, not in euros from the accounts.
• Convert the bottles into kilos using the density of each product: 1.465 g/mL for desflurane, 1.52 for sevoflurane, 1.496 for isoflurane.
• Multiply each mass by an IPCC GWP, assuming 100% of the gas is released: the 2021 values (2,590, 195, 539 and 273), or the 2013 values that many factors still use (1,790, 216, 491 and 265).
• Choose the category, direct emissions or purchases, then write it into the assessment's methodology and keep it from one year to the next, like the GWP chosen.

This method takes ADEME's rule for N2O, extends it to halogenated agents and states which GWP it uses, which makes it readable by an external verifier. The resulting figure then feeds into the establishment's transition plan: among the levers for reducing a carbon footprint, it is one of the few where a decision taken in theatre shows up from the following year.

3Desflurane: what does the 2026 EU ban change for hospitals?

Regulation (EU) 2024/573, in force since 11 March 2024, also covers air conditioners and heat pumps. Its Annex II brings halogenated anaesthetics within its scope, but it restricts the use of desflurane alone, the agent with the strongest warming effect. Sevoflurane and isoflurane remain usable without conditions.

The provision and its derogation

Article 13(8) consists of 2 sentences. The first prohibits desflurane from 1 January 2026, except where its use is strictly necessary and no other anaesthetic can be used for medical reasons. The second sets the hospital's only obligation: it must keep evidence of the medical justification and provide it on request to the national authority or to the European Commission.

Official Journal of the EU, 20 February 2024

The article that prohibits desflurane

Regulation (EU) 2024/573 of 7 February 2024 on fluorinated greenhouse gases, Article 13(8). Cited document.

Paragraph 8 of Article 13 consists of 2 sentences: the prohibition and its only derogation, then the evidence the establishment keeps. Capture of the gas does not appear in it: it is mentioned only in recital 27, in the conditional.

The text goes no further. Recital 27 expresses the wish that any desflurane still used be captured, but only as something that should happen: no article requires capture in theatre. Article 4 prohibits the intentional release of a fluorinated gas where it is not technically necessary, without expressly referring to anaesthetic gases. Penalties are a matter for each Member State, which had to notify its rules to the Commission before 1 January 2026.

What evidence must be kept

The European Commission specifies the form of this evidence: a written medical justification, kept for 5 years, for example in the clinical record of the procedure. The doctor needs no prior authorisation. Nor does the hospital have anything to report, since the annual reporting under the regulation is aimed at producers, importers and exporters.

In practice, an establishment that keeps a few bottles must be able to explain, case by case, why sevoflurane or intravenous anaesthesia was not suitable. A list of indications approved by the anaesthesia team, and a line in the record of each patient concerned, make it possible to answer a request from the authority.

The English precedent

In the United Kingdom, NHS England, which runs the National Health Service in England, moved ahead of the European Union. The end of desflurane in routine practice was set for 1 April 2024 in its guidance on desflurane decommissioning, with an exception for certain long cranial neurosurgery procedures. It was the first time the English health service had given up a commonly used medicine because of its effect on the climate. The withdrawal happened in stages:

• Nearly 90 English NHS trusts had stopped using desflurane completely by the time of the March 2024 guidance.
• According to the NHS review of its 5 years of greener NHS work, published in September 2025, emissions from desflurane have fallen by 41 ktCO2e, or 98%, since 2019-2020.

4Nitrous oxide: why decommission piped networks?

In many hospitals, N2O does not reach the theatre in cylinders. It is stored in a manifold, a bank of linked cylinders, then distributed through pipework to the wall outlets in each theatre.

Leaks

The measurement that SFAR cites comes from Australia. A study published in 2022 compared, in a Melbourne hospital, the N2O leaving the manifold with the N2O administered to patients. According to SFAR, which cites it, leaks exceeded 75% of actual consumption. No French national measurement has been published.

The French Hospital Federation (FHF) called on 11 October 2024 for these networks to be shut down for good. Its 2 figures should be read with caution. According to the FHF, hospital N2O would generate more than 100,000 tCO2e a year in France: the conditional is the FHF's own, and the method is not published. Its figure of 80% leakage repeats the order of magnitude of the Australian study.

SFAR, for its part, does not call for dismantling in its 2022 guidelines. It suggests preferring cylinders to piped supply, where N2O is still used. The statement that SFAR therefore calls for all existing networks to be dismantled is the FHF's, made in 2024.

French hospitals that have shut off their networks

Several French hospitals have stopped supplying their networks and publish the results:

• Toulouse University Hospital (CHU de Toulouse) avoids about 1,000 tonnes of CO2 a year, or 36% of the emissions linked to N2O and its mixture with oxygen. The figure comes from its page on shutting off the networks, updated in March 2026.
• Pau hospital (centre hospitalier de Pau) stopped nitrous oxide in theatre on 18 April 2025, with its wall networks shut off, while keeping the oxygen mixture in cylinders in a few departments. It expects savings of nearly €5,700 a year.
• At AP-HP, dismantling the wall networks reduced piped N2O consumption by a factor of 3 between 2024 and 2025, according to its page on its Bilan Carbone®.

These figures, mostly drawn from volumes ordered, show the effect of the shutdown without measuring the leak itself. Across England, the NHS puts the N2O emissions avoided compared with 2019-2020 at more than 80 ktCO2e, in its 5-year review.

The main supplier is following suit. In a June 2025 press release, Air Liquide Santé France set itself the target of ending sales of the cylinder banks and large cylinders that supply medical N2O networks by the end of 2026. A hospital it supplies that keeps its network will have to rethink how the gas reaches the theatre.

5What do French anaesthetists recommend?

In September 2022, SFAR published, with the French Society for Hospital Hygiene and the French Society of Clinical Pharmacy, 17 recommendations to reduce the environmental impact of general anaesthesia. All are expert opinions with strong agreement, the lowest level of evidence in the method used.

Choice of agent and fresh gas flow

The recommendations on inhalational anaesthesia always apply where the clinical benefit for the patient is equal:

• Use sevoflurane in preference to desflurane or isoflurane for inhalational anaesthesia.
• Do not use nitrous oxide, and if it is used, prefer a cylinder to the pipeline network.
• Work at low fresh gas flow, between 0.5 and 1 litre per minute according to the definition used in the supporting rationale.
• Prefer the automated mode of anaesthesia ventilators, which reduces CO2-equivalent emissions by around 40% according to the rationale.
• Monitor the depth of anaesthesia, with the share of vapour in exhaled air, to consume less anaesthetic vapour.

Intravenous anaesthesia

SFAR does not rank intravenous anaesthesia with propofol above inhalation: it asks for the 2 to be used interchangeably. Propofol is not a greenhouse gas, but SFAR recognises its ecotoxicity for soil and water. Studies diverge on its carbon footprint:

• A 2012 study found propofol emissions nearly 10,000 times lower than those of desflurane, over its life cycle.
• A 2021 study, cited by SFAR, found it equivalent to sevoflurane delivered at the lowest flow, with 70% of vapours recaptured.

Vapour capture

On the capture and recycling of halogenated agents, SFAR makes no recommendation: the data did not allow these systems to be compared with conventional scavenging, either for safety or for the environment. At the end of 2022, only one system was available in France, according to the journal Risques & Qualité, and its efficiency had yet to be established.

For us at Projet Celsius, the gas item is the one that can be dealt with fastest in a hospital's footprint, and also the one that is counted least accurately. The useful question is how many kilos of each gas the hospital buys, with which GWP and under which category they are counted. The other theatre levers, such as the switch to reusable devices or the eco-design of care, require a life cycle assessment. This one is decided on a pharmacy order. We recommend extracting the quantities from the pharmacy, writing the method into the assessment, then comparing each year the N2O ordered with the N2O administered in theatre: the gap shows what the network loses.

6Key takeaways

• One kilo of desflurane released counts as 2,590 kilos of CO2e over 100 years, one kilo of nitrous oxide as 273, and that gas stays in the air for 109 years.
• In a Bilan Carbone®, a bottle of desflurane weighs from zero to close to a tonne of CO2e depending on the method and GWP chosen, which must be written down and kept stable.
• Desflurane has been prohibited as an anaesthetic in the European Union since 1 January 2026, unless medically necessary and justified in writing, evidence to be kept for 5 years according to the Commission.
• Piped wall networks for nitrous oxide lose a large share of the gas purchased, and Air Liquide aims to stop selling the cylinder banks that supply them at the end of 2026.
• SFAR recommends low-flow sevoflurane, without nitrous oxide, and puts intravenous anaesthesia on an equal footing with inhalation.

The weight of gases among a hospital's other categories, from medicines, whose carbon score is entering tenders, to energy, is set out in our article on a hospital's Bilan Carbone®.

Further resources

Frequently asked questions

1Why has desflurane been banned in the EU?

Because it has a strong warming effect: one kilo of desflurane is equivalent to 2,590 kilos of CO2 over 100 years, according to the IPCC, and the gas is released almost entirely into the air after anaesthesia. Regulation (EU) 2024/573 on fluorinated gases has prohibited it as an anaesthetic since 1 January 2026, as other agents, such as sevoflurane, warm the climate far less.

2Can desflurane still be used in France and the rest of the EU?

Yes, but only where it is strictly necessary and no other anaesthetic can be used for medical reasons. The establishment keeps the written medical justification, for 5 years according to the European Commission, for example in the patient's record, and provides it to the authority on request. No prior authorisation is required of the doctor.

3What is the carbon footprint of nitrous oxide?

One kilo of nitrous oxide released warms the climate as much as 273 kilos of CO2 over 100 years, and the gas stays in the atmosphere for 109 years, according to the IPCC Sixth Assessment Report. It is not fluorinated, so the EU F-gas Regulation does not cover it. In hospitals with piped wall networks, a large share of the gas purchased is lost through leaks before it reaches the patient.

4Are anaesthetic gases counted in the French BEGES emissions report?

Nitrous oxide is: it appears on the list of gases set by the ministerial order of 25 January 2016. The halogenated agents, desflurane, sevoflurane and isoflurane, do not literally appear on it, and ADEME's 2019 health-sector guide does not count them. Some hospitals, such as AP-HP, nonetheless count them in their purchases: the method chosen must be written into the assessment.

5Which anaesthetic gas has the lowest climate impact?

Among halogenated agents, sevoflurane: its GWP is 195, against 539 for isoflurane and 2,590 for desflurane, and it stays in the air for only 1.9 years. The French Society of Anaesthesia and Intensive Care Medicine recommends preferring it, at low fresh gas flow (0.5 to 1 litre per minute according to its rationale), and without nitrous oxide.

6Is intravenous anaesthesia better for the climate?

Injected propofol is not a greenhouse gas, but the French Society of Anaesthesia and Intensive Care Medicine recognises its ecotoxicity for soil and water. Its 2022 guidelines therefore ask for it to be used interchangeably with inhalation, for equal clinical benefit. A 2012 study found its emissions far lower than those of desflurane; a 2021 study found it close to low-flow sevoflurane with vapour recapture.

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