At Changi General Hospital (CGH), Dr Michelle Tan and her team tackled a hidden source of emissions – wasting nitrous oxide (N₂O) used in Anaesthesia. By switching to a portable small-cylinder system and decommissioning the hospital’s central pipeline, they achieve a dramatic reduction in greenhouse gas emissions and costs, while maintaining safe and effective patient care.
The Challenge
Nitrous oxide commonly known as laughing gas, has been as an anaesthetic for over a century. But, it is also a potent greenhouse gas - 273 times more damaging than carbon dioxide – and contributes to ozone layer depletion.
Globally, studies show that 70–95% of N₂O is wasted through hospital pipelines and manifolds system before ever reaching a patient.
At CGH, Dr Michelle Tan and her team used Electronic Health Record (EHR) anaesthesia data to investigate local usage patterns. They found that up to 74% of N₂O was wasted annually, amount to more than 800 tonnes of CO₂e emissions over two years.
The Approach
By comparing EHR0-tracked N₂O usage with procurement records, the team was able to quantify waste and identify the hospital’s central manifold pipeline system as the key source of wastage.
In 2024, CGH decommissioned its N₂O manifold system and introduced a new set up: portable cylinder tanks attached directly to anaesthesia machines in each operating theatre. This reduced the distance gas needed to travel and minimized leak points, while maintaining a safe and steady supply for clinical use.
The Impact
The intervention led to 94% reduction in nitrous oxide wastage and avoided over 400 tonnes of CO₂e emissions each year – the same as 6,700 cars driving from Singapore to Kuala Lumpur. The hospital also saw significant cost savings as a result of reduced gas loss.
Because the approach relies on readily available EHR data and off-the shelf cylinder systems, it offers a replicable and scalable model for other hospitals across Singapore and beyond.
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For more information
Utilising electronic anaesthesia records to audit nitrous oxide consumption and waste, and implementation of a loss monitoring system, British Journal of Anaesthesia, 2025
Acknowledgements
The Centre for Sustainable Medicine would like to thank Dr Tan, Dr Ang, Nurse Gurdip, Ms Ong, Mr Sridharan, Mr Tiang and the whole medical team for leading the transition, as well as to the Communications team at Changi General Hospital for their invaluable support.