Nitrous usage in new hospitals

Chris Allen's picture

Hi everyone,

I would be really keen to hear from anyone here who's had experience working in new-build hospitals recently.

Part of my work about nitrous oxide use is around manifold/pipeline wastage, and I had wondered if there is perhaps a correlation with moving to a new hospital (and therefore hopefully better piping etc!) and an otherwise unexplained reduction in nitrous oxide use? 

It would involve a bit of digging around with the estates and pharmacy departments, but hopefully would be an interesting project to demonstrate that nitrous waste from the manifold end is an issue that needs addressing?

Happy to chat in more detail of course, so please do get in touch. Any other thoughts and ideas are welcome as well. Thanks!



Nitrous Wastage

Matthew Jenks's picture

Hi Chris, this is really interesting, I did a carbon footprint of our hospital and N20 was approx. 12% of our total carbon footprint ( 3432 tonnes of C02 equivalents) Mainly G cylinders from two banks of cylinders reticulated to hospital wall outlets. Use mainly occurs in our maternity unit and theatre block. Benchmarking against other hospitals in NZ showed we were an outlier (our hospital is > 50 yrs old). A pressure test of piping turned up nothing. Our N20 use has since dropped to 2144 tonnes of C02 equivalents in 2019 and i cant explain this difference. We hardly use any in theatres (paeds gas inductions only). In maternity we have shifted to more portable cyclinders with entonox mixers and less piped gas to mixers. Perhaps it is a manifold problem, i didnt realise this was a problem with other hospitals? We are currently in the process of planning a new $1.4 billion dollar hospital. I am suggesting strongly that we dont reticulate N20 to maternity or theatres and rely on portable cylinders. Also suggesting we investigate N20 scavenging and destruction in maternity unit (as they do in Sweden). Would be interested to discuss more.


Great work!

Amarantha Fennell-Wells's picture

Hi Matthew, I am looking to work with Chris on some similar aspects of usage of N2O in a hospital in South Wales, UK. The mysterious reduction in CO2e by over a third is shocking. I would love to speak with you regarding your methods of investigation to ascertain your data, as well as scavenging and destruction modules to help plan your new hospital.


Possible explanation?

Tom Dolphin's picture


I'm interested to find this thread. I've asked our Pharmacy how much nitrous we used in 2019/20 and the answer is apparently 344 size G cylinders and 52 size E cylinders plus change, giving a total of 3 million litres of nitrous use per year.

Across three hospitals, that means something like 24 theatres running 1L/min flow of nitrous continuously for 8 hours a day, Mon-Fri for 52 weeks a year... which is wildly outside the bounds of reality.

So where is all the nitrous being used? We don't do dental, and our Entonox is provided separately to Labour Ward and not included in that figure, so I'm at a loss to know where it's all going.

I've approached Pharmacy to confirm the figures and check that I'm not imagining it and we are really not using that much, and will approach Estates in case the problem is leakage as has been suggested here.


Possible explanation

Janet Smith's picture

Hi Tom,

Leakage in the manifold and the distribution system can be a factor.  We inspected our nitrous and entonox storage and distribution system this morning.  What we've learned are:

  • the distribution system is automated which monitors the content of each cylinder and switches to the next one in the array once the one in use is empty. 
  • there is a robust gas leak monitoring system installed in each plant
  • each cylinder has a 3 years best before date which means they need to be changed every 3 years.  In a plant with very low demand, a number of cylinders will go out of date without being used.  those cyclinders are counted as in the usage.
  • Some of the services that uses nitrous oxide surprised us because they are not what you'd usually include in a list

Oh that's very interesting,

Tom Dolphin's picture

Oh that's very interesting, thank you. I shall bear that in mind when discussing with Estates.


What kind of services are using nitrous other than theatres? I'm intrigued!



Radiology, Dental, Endoscopy

Janet Smith's picture

Radiology, Dental, Endoscopy among others


Thanks, will bear that in

Tom Dolphin's picture

Thanks, will bear that in mind.



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