Where should medical gas pipes not be routed?

The routing rules sit mainly in chapter 15 of HTM 02-01 Part A (2026 edition), the NHS England guidance on medical gas pipeline systems; other countries apply their own codes.

Places to keep pipes out of

• Exposed pipes: lift shafts, kitchens, laundries, boiler houses, generator rooms, incinerator rooms, storage rooms designed for combustible materials and any other fire-risk area.
• Areas where the pipes may suffer mechanical damage, chemical damage or excessive heat, or splashing, dripping or permanent contact with oil, grease or bituminous compounds, or electrical sparks.
• Close to natural gas pipelines, where a leak could let flammable gas accumulate.
• Enclosed ducts shared with other services where the pipes cannot be inspected.
• Inside the area that an area valve service unit (AVSU) isolates, for the mains that feed it, unless extra protection is added: pipelines supplying AVSUs should come from outside the fire compartment being protected (see zone valve box location).

Where a run through a hazardous area cannot be avoided, the pipes should be enclosed in non-combustible, non-corrosive materials that have no electrolytic reaction with copper.

Routes that need extra care

• Shared ducts: in ducts with steam mains or water services, pipes should be inspected annually, because chloride deposits after a leak can corrode them. Ducts or voids holding valves or other mechanical connections should have adequate ventilation; runs brazed along their entire length and fully pressure-tested need none.
• Clearances: at least 25 mm between services, and at least 150 mm between medical gas pipes and heating, hot water or steam pipes.
• Electric cables: routes should keep the pipes from touching cables and wiring (see bonding and earthing).
• Walls and floors: pipes should not be concealed in walls or encapsulated in floors; where that cannot be avoided, the route should be clearly shown on the as-fitted drawings. Stud or plasterboard partitions are acceptable if the pipes are protected against corrosion and damage such as drilling.
• Outside and underground: external runs should be avoided wherever practicable, and buried lines should run in appropriately drained ducts of at least 450 mm by 450 mm with removable covers.
• Inside the building: internal pipes should be protected where trolleys and tugs could damage them.
• Treated timber and MRI suites: pipework may corrode in contact with timber treated with fire-retardant compounds, and MRI suites may need waveguides to keep their radio frequency shielding intact.

In Portugal, the ACSS specification ET 03/2006 (revised 2024) asks for all pipe runs to be installed with access for repair and maintenance in mind.