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Entonox, more commonly known as 'gas and air', is a mixture of 50% oxygen and 50% nitrous oxide gas. It can help reduce pain during labour and make it more bearable. 

Entonox® (also known as gas and air ) is a mixture of nitrous oxide and oxygen used to relieve pain.  

Entonox® is a gas that you breathe in via a mouthpiece or facemask when you need it.   You are in control the amount of Entonox you use, but to get the best effect it is important to get the timing right. You should start breathing Entonox® as soon as you feel a contraction coming on to get the full effect when the contraction is at its peak. You should then stop using Entonox as the contraction ends, breathing normal air between your contractions.

Entonox® is the most common pain relief for labour. People like it because:
·    It works quickly and wears off in minutes
·    It will not take the pain away completely, but it may help you feel more relaxed
·    It has no harmful effects on your baby
·    You can use it at any time during labour

Entonox® has been used safely for pain relief for labour for many years.  The common side effects are generally mild and go away quickly when you stop using it.  These include:
·    A dry mouth
·    Feeling sick (nausea) and vomiting
·    Feeling dizzy, light-headed or sleepy
Having a break from using Entonox in between contractions helps to reduces these unwanted effects.

Entonox® is a greenhouse gas so contributes to global warming. With greater awareness about air pollution and our need to look after the environment, some maternity units are introducing new technology (cracking) that breaks down Entonox® into harmless gases to reduce the impact of its use on the environment. If you would like more information about this, please see our information on your pain relief for labour and the environment.
Long-term exposure (over weeks and months) to high levels of Entonox can potentially cause health problems. This is not an issue for people using it for a matter of hours during labour and birth, but could be a problem for healthcare workers. Clinical areas using Entonox need to monitor levels of it to ensure that they are safe for staff working there. In some exceptional circumstances if levels are very high, a maternity unit may need to suspend the use of Entonox until the environment is made safe for the staff working there. If this happens, you should have other pain relief options available to use.