What is a third-source or fourth-source manifold panel?

Three sources is the minimum

HTM 02-01, the NHS England guidance (2026 edition), says that, in accordance with BS EN ISO 7396-1, all medical gas supplies should comprise three sources of supply; ISO 7396-3 (2025) also leaves the rule of at least three sources to ISO 7396-1. The names and roles differ between documents:

HTM 02-01 also classifies a cylinder manifold, whatever its number of banks, as a single source of supply, and acknowledges that such classifications differ.

Beyond the three sources

HTM 02-01 allows for a critical emergency supply where the design identifies areas that need resilience beyond the three standard sources. It is a manifold upstream of the area's zone valve (AVSU), feeding through a non-return valve on the main pipeline. It should come on automatically when the primary, secondary and tertiary sources are empty or fail, prevent oxygen flowing back into the rest of the pipeline, and allow cylinders to be changed while the flow is maintained. Its alarm is displayed in that zone and repeated at the area occupied 24 hours a day.

What HTM 02-01 asks of manifold panels

• Under HTM 02-01, every manifold control panel should pass the full pipeline design flow of the system it supplies.
• Each emergency reserve bank signals reserve low below a nominal 1400 kPa for liquid cylinders, or below 50% of the available volume for other gases.

Ultra Controlo lists third-source and fourth-source control panels for medical gas cylinder manifold systems.