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A project at St Bartholomew’s Hospital set out to reduce nitrous oxide wastage from an extraordinary 98.5% to just 5% by March 2025.

Nitrous oxide, while commonly used in anaesthesia, is also a powerful greenhouse gas. Reducing its usage and overall waste is a key part of both NHS England and our own green plans.

In 2023, Barts Health was the highest user of nitrous oxide per operation in the UK, producing 44kg of CO2 compared with a national average of 17kg.

At St Bartholomew’s, the gas was supplied through a piped system from large external cylinders.

In response, an analysis comparing how much nitrous oxide was purchased with how much was used clinically took place across our Trust. This revealed a large discrepancy, suggesting leakage from the piped system. A project team at St Bartholomew’s identified where nitrous oxide was still clinically required and led the transition to a new approach. Following divisional approval, a successful pilot was run, working closely with Estates, Skanska, our operating department practitioners and both Health and Safety and Clinical Engineering teams.

The pilot confirmed that removing machines from the piped system did not trigger medical gas alarms and had no impact on clinical safety or performance. With full sign-off from all teams, the new approach was rolled out across the hospital.

Theatres completed the switchover in February 2025, followed by cath labs in March 2025. Wall-mounted nitrous ports were capped, the piped system decommissioned, and large external cylinders permanently removed. Funding of £15,000 for estates works was secured from NHS England, and the project will deliver ongoing annual savings of £11,000 as well as significantly reducing the site’s greenhouse gases.

Andrew Wragg, medical director at St Bartholomew’s, said:

This achievement highlights the power of clinical leadership and collaboration to deliver meaningful environmental change, improving sustainability, reducing costs, and maintaining the highest standards of patient care.

St Bartholomew’s was the first hospital to complete the switch-off, with Whipps Cross and Newham hospitals following closely behind. The Royal London Hospital is currently working towards a complete switch-off.

Henna Roberts, senior change manager, added:

The nitrous oxide project is part of ongoing efforts to deliver on our green objectives. If you have any ideas or are delivering green projects you’d like to share, please do get in touch.

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• Sustainability at Barts Health