Nix the Nitrous

This is a summary written by Alifia Chakera - Pharmacist at NHS Lothian. Alifia has led this research into nitrous oxide mitigation alongside University of Edinburgh. This is an initiative coined 'Nix the Nitrous' which we are keen to help share across the healthcare system. Mitigating nitrous oxide waste requires a truly multidisciplinary approach with involvement from pharmacy teams being key. We'll be sharing more resources on the Green Health Wales site in the coming months, but in the meantime you can find more information here, get in touch with the team at and connect with Alifia online @AlifiaChakera


Nitrous oxide is a potent greenhouse gas and dominant ozone depleting substance. Within healthcare it is used ubiquitously as an anaesthetic agent by a variety of practitioners in a number of settings. Within the UK emissions from nitrous oxide products within NHS sites approximated at least 319.4 Kilo tonnes in carbon dioxide equivalents (KtCO2e) in 2019/201.

Research from Scotland has revealed that wastage within piped nitrous oxide systems is a significant problem. In 2020, a small initial study in two NHS Lothian hospitals revealed piped nitrous oxide wastage to a total volume approximating 1.5 million litres per annum.

Due to the significance of the findings, the mitigation methods applied by the Scottish team have been escalated across the UK and into the Republic of Ireland. This has been facilitated by The Nitrous Oxide Mitigation Project which has already provided a number of compelling case studies all demonstrating significant waste from piped nitrous oxide including that of Entonox® manifolds. By 31 March 2021, 16 sites have estimated a total waste of piped nitrous oxide of 13.7 million litres per annum or 95% of the total collective annual volume. A further three sites estimated an annual Entonox waste® to a collective volume 10.6 million litres

The Greener NHS programme has commissioned an evidence-based policy report to provide structured guidance that will enable NHS England sites to mitigate this nitrous oxide waste. This report, which will be made available summer 2021, will be of value to the rest of the UK and Republic of Ireland. One of the main features of report is the importance placed on securing quality nitrous oxide data and meaningful interpretation of this data to determine, implement and monitor interventions.

The report’s main recommendations have been developed through the evidence gathered by the nitrous oxide mitigation project and national stakeholders and are intended to remove excessive redundancy with the nitrous oxide and Entonox® systems as well as mitigate supply chain wastage within NHS sites.

Below is summary of its key recommendations.


1. Medical Gas Committees (MGCs) should establish multidisciplinary project teams to work toward net-zero emissions for all clinical areas relying on nitrous oxide products.

2. All acute sites with a piped nitrous oxide and Entonox® systems should undertake a waste review3.

· Qualitative and/or Quantitative Clinical assessment of nitrous oxide usage within theatres and other areas and compare this to total volume.

· Review supplier cylinder returns data to calculate volume consumed

· Determine Entonox® in CO2e per maternity and benchmark this against typical values

3. Estates and MGCs should immediately investigate system waste


· Stock management and security

· System leaks at manifold, from outlets or piped infrastructure

· System design: pressure set to high


· Support above actions and

· Review wasteful clinical practices including leaving flow valves in situ and failing to terminate nitrous oxide through anaesthetic machines.

4. The leanest nitrous oxide supply should be introduced.

· Removing superfluous piped infrastructure

· Decommissioning redundant manifolds

· Introduce a portable supply to areas with continued clinical need

· Manifolds may benefit from the introduction of flow meters.

5. MGC quarterly reviews of processes and practices to minimise waste reducing to biannual after 12 months

· Greener clinical practices across all specialties using anaesthetic gases.

· Consideration of green technologies such as nitrous oxide cracking technologies for manifold Entonox®.

6. New theatres should be built to have zero-emissions and should avoid excessive system redundancy. Nitrous oxide piped systems should not be routinely introduced in new surgical suites.


1 - BOC 5 Nation Data, UK extract 2019/20 2 Chakera, A. Reducing Nitrous Oxide Emissions in 2 - NHS Lothian, Dissertation University of Edinburgh, July 2020

3 - The Nitrous Oxide Mitigation Project A. Chakera, A. Fennel-Wells and C. Allen