# What is an emergency supply inlet on a medical gas network?

**What is an emergency supply inlet or emergency box on a medical gas pipeline?**

An emergency supply inlet is a valved connection on a medical gas pipeline through which a temporary or mobile supply can feed the network during emergency repairs, modifications or a supply failure. An emergency box, in the sense of a zone valve box, is used to shut gas off instead.

HTM 02-01 Part A, the NHS England guidance on medical gas pipelines (2026 edition), describes three ways of feeding a pipeline from outside its fixed sources.

## Temporary inlet port

A connection point for a temporary supply to support the system during emergency repairs or modifications. Where provided, it is located downstream of the main source of supply line valve isolation point, is sized for full flow, and comprises a line valve assembly, an additional non-return valve on the temporary inlet side and a connection that can be blanked.

## Emergency inlet port for oxygen

HTM 02-01 asks for emergency inlet ports to be considered during design. A fixed manifold system may remove the need for one; at the time of writing, mobile vacuum-insulated evaporators (VIEs) were not readily available for immediate delivery and connection to such ports; and HTM 02-01 says adequate resilience in the design of the system should eradicate the need for them.

## Backfeed through a NIST or terminal unit

In emergencies or planned shutdowns, trained engineering staff may backfeed the pipeline through a NIST connector or a terminal unit, using a kit of at least two cylinders, one on each bank, with individual regulators and gas-specific hoses. A kit connected downstream of a closed zone valve (AVSU) can support a department, usually with limited capacity compared with a fixed automatic manifold, and at high flows icing of regulators and hoses may cause supply failure.

Non-return valves prevent backflow: for medical air, HTM 02-01 places one upstream of any inlet point that may be used to feed the system in an emergency.

## Emergency box versus emergency inlet

WHO, in Foundations of medical oxygen systems (2023), describes zone valve boxes that first responders can open in an emergency, such as a fire, to close the valve. The Emergency Box from Ultra Controlo is of this type: an emergency isolation box for rapid manual shutdown of the gas supply to individual zones.

For feeding gas in, Ultra Controlo supplies a maintenance supply assembly for temporary gas delivery while the permanent supply is serviced, so that clinical areas can remain operational; an emergency oxygen supply system for backup delivery when the primary pipeline source fails; and the ULTRAGEC emergency cabinet, which connects by derivation to the secondary networks upstream of a critical area. According to its datasheet, the ULTRAGEC 2 holds 2 B50 cylinders and the ULTRAGEC 4 holds 4, each cabinet with a 40 m³/h vacuum pump.

### Where is a temporary inlet port installed?

HTM 02-01 places it downstream of the main source of supply line valve isolation point, sized for full flow.

### Is an emergency inlet port mandatory?

Not in HTM 02-01, which asks for it to be considered during design and says adequate resilience in the system design should eradicate the need for it.

## Sources

- [NHS England, HTM 02-01 (2026) Part A, paragraphs 4.39 to 4.41, 5.82, 5.83, 6.97, 7.59 and 15.185 to 15.187](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-a-design-installation-validation-verification-aug-2026.pdf)
- [WHO, Foundations of medical oxygen systems (2023), section 2.9.4](https://iris.who.int/server/api/core/bitstreams/4ad6f5fd-089e-4142-8439-b64e98d816d8/content)
- [ultracontrolo.com: Emergency Box for Medical Gas Pipeline Systems](https://www.ultracontrolo.com/accessories/emergency-box)
- [ultracontrolo.com: Maintenance Supply Assembly for Medical Gas Lines](https://www.ultracontrolo.com/accessories/maintenance-supply-assembly)
- [ultracontrolo.com: Emergency Oxygen Supply System for Hospitals](https://www.ultracontrolo.com/accessories/emergency-oxygen-supply-system)
- [Ultra Controlo, ULTRAGEC datasheet, pp. 2 and 4](https://www.ultracontrolo.com/products/ultragec)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/answers/what-is-an-emergency-supply-inlet/