Does every ward need dual circuits?

No. In HTM 02-01 Table 1, general in-patient wards, day patient and out-patient areas are typically single circuit; dual circuits are listed for spaces such as critical care bed spaces, resuscitation rooms, operating theatres and neonatal cot spaces.

Is a ring main required?

HTM 02-01 says the distribution network should use ladder systems and ring mains where practically possible; with line valve assemblies, a ring main lets individual segments be isolated without major disruption to wards.

What keeps a critical area supplied if its pipeline fails?

In Portugal, the ACSS specification asks for a permanently connected reserve unit next to theatres and intensive care that starts automatically if the central supply fails; HTM 02-01 relies on dual circuits and on secondary and tertiary sources.

What pipeline redundancy do critical care areas need?

Q: Do operating theatres and ICUs need dual or looped medical gas feeds, and what redundancy do HTM 02-01 and Portugal's ACSS specification ask for?

In NHS England's HTM 02-01 (2026), the typical provision for intensive care, high-dependency and coronary care bed spaces, resuscitation rooms and operating theatres is a dual pipeline circuit, with terminal units on each side of the bed, or on each pendant, fed from separate A and B circuits.

Do operating theatres and ICUs need dual or looped medical gas feeds, and what redundancy do HTM 02-01 and Portugal's ACSS specification ask for?

HTM 02-01, the NHS England guidance for medical gas pipeline systems, achieves continuity of supply by installing duplex components as a minimum and by keeping the system running under a single fault condition, meaning one defective device or one abnormal external condition. Loss of supply during planned maintenance of a source is not counted as a single fault.

Dual circuits at the bed and in theatre

Table 1 of HTM 02-01 Part A lists dual circuits as the typical provision for, among others, intensive care, high-dependency and coronary care bed spaces, emergency department resuscitation and major treatment spaces, neonatal cot spaces, and acute, day case, minor operations and ophthalmic theatres.
In critical care areas the circuits should be distributed on both sides of the bed, and where dual circuits are stated they should be split evenly to cover both sides of the bed or each pendant.
Dual pipeline circuits should be provided to operating theatres where enhanced resilience is required at the point of surgery, and each theatre pendant may be served from a separate circuit so that supply stays available if one circuit is isolated or fails. Anaesthetic rooms may be served from one of the theatre circuits where the informed design process and a local risk assessment support it.
In critical care areas, terminal units on dual circuits should be identified with the circuit number of their area valve service unit (AVSU), for example A and B, and where wall space allows, a two-column AVSU arrangement with a local alarm for each column is preferred because it reduces confusion during isolation.

Ladders, ring mains and flow loops

HTM 02-01 notes that the high flows of the COVID-19 pandemic highlighted the risk of starving terminal units downstream of a large load, and that ladder arrangements, ring mains and flow loops can give greater resilience. It recommends ladder systems, with two or more interconnected risers to each floor, and ring mains where practically possible. A ring main can be fed from either leg of the ladder (where installed) and from either direction, and its line valve assemblies allow one segment to be isolated for additions or maintenance without major disruption to wards. Flow loops can be used in bed bays to maintain continuity of flow, and in critical care with high-flow ventilation the loop should be increased by one pipe size.

Sources of supply and buried lines

Following EN ISO 7396-1, HTM 02-01 says every medical gas supply should comprise primary, secondary and tertiary sources (see supply sources). On a large oxygen system there may be several automatic changeover manifolds providing continuity of supply to critical care areas and theatres separately from the general areas. Where an underground line cannot run in a duct with removable covers, two pipes should be laid in separate trenches at least 2 m apart, each able to carry 100% of the design flow, with line valve assemblies at each end for individual or dual feeding.

Portugal: ACSS ET 03/2006

The Portuguese ACSS specification ET 03/2006 (revised 2024) asks for dedicated branches to be considered for intensive care and operating theatres, and for each service to be fed by at least two second-stage pressure reduction sets in bypass. For its most critical services, theatres and intensive care, it asks for permanently connected, redundant reserve supplies of oxygen, medical air and vacuum that start automatically if the central supply fails: a compact unit next to the service with a vacuum plant, oxygen and medical air each from a service cylinder and an emergency cylinder with automatic changeover, and an alarm connected to the building automation system. It also recommends that all intensive care and emergency observation beds be able to take high-flow oxygen, and a dedicated network, fed directly from the manifold or in a ring, for the services named in that section (intensive care, in-patient wards and emergency).