This beggars belief. Why has this happened? Consider the consequences and complications of not having basic pain relief, so going straight to morphine and epidurals, interventions, assistance, and emergency caesarean.

https://www.itv.com/news/meridian/2022-11-26/women-in-labour-not-to-be-given-gas-and-air-at-hospital-after-ventilation-issue

East Kent Hospitals Maternity
November 25 at 5:11 PM ·
We regret and are sorry to tell you that women in labour at our maternity department at William Harvey Hospital will not be able to access Entonox (gas and air) at the moment.
Due to a ventilation issue, the current levels of gas in the air could affect the health of staff who work for long periods in the labour rooms. Mums and babies are not at risk of harm.
We are very sorry if you are affected by this. We will still be able to offer you every other method of pain relief. If you are due to give birth at William Harvey Hospital, please talk to your midwife about your options. You can also find pain relief advice on the Bump, birth and beyond website.
We expect to be able to use Entonox again within two weeks.
What has happened?
Checks to make sure maternity staff are working safely with Nitrous Oxide (a gas present in Entonox) have shown that some staff may have been exposed to high levels of Nitrous Oxide.
What is Nitrous Oxide?
Nitrous Oxide is a gas found in Entonox, a gas mainly used in the maternity units for patient pain relief in childbirth (often called gas and air). There may be low levels of Nitrous Oxide in a healthcare environment as it is a commonly used medical gas.
What are the potential effects of Nitrous Oxide exposure?
Short-term exposure is not a problem, and so mums and babies are not at risk.
What is going to be done?
New ventilation systems for the maternity unit have been ordered and the environment will be continually monitored.
Can I still have gas and air if I have a homebirth?
Yes, gas and air is still available for homebirths. This issue is only affecting William Harvey Hospital.