Sizing MGPS for an ICU Expansion

When a hospital adds critical-care beds, the first instinct is to multiply the new bed count by a per-bed flow and add it to the existing plant. That approach misses how ICUs actually use medical gases — and it is the most common reason expanded systems run short at peak demand.

Critical care changes the demand profile

General ward outlets are used intermittently. ICU outlets are not. Ventilated patients, continuous suction and high-flow oxygen therapy mean a much larger share of outlets are in use at the same time, for longer. The design question is not “how many outlets?” but “how many outlets will be drawing gas simultaneously, and at what flow?”

Diversity factors drive the answer

Recognised medical gas design guidance (for example ISO 7396-1 and HTM 02-01) sizes systems using diversity — the proportion of outlets assumed to be in use at once. Critical-care areas carry much higher diversity than wards. Applying ward-level assumptions to ICU beds is where most under-sizing starts.

A sound sizing exercise therefore:

• Separates demand by department, applying the appropriate diversity to each.
• Treats each gas on its own terms — oxygen, medical air and vacuum have different usage patterns and peaks.
• Checks the whole system, not only source capacity: pipe sizes, zone valves and alarm points must carry the new flows within acceptable pressure drop.

Don’t forget the existing plant

An expansion is connected to a system that is already working. Before sizing additions, the existing source equipment, pipework and actual consumption should be surveyed. Older distribution pipework sized for a smaller hospital can become the bottleneck even when new source plant is adequate.

Design the risers for tomorrow

Healthcare facilities rarely stop growing. Oversizing main risers modestly and providing valved, capped connection points for future zones costs little during construction and avoids disruptive shutdowns later. The same thinking applies to manifold rooms and plant space.

Test before you trust

Every new or modified section must be pressure-tested, checked for cross-connection and tested for gas identity and purity before it is put into clinical use. Commissioning documentation then becomes the baseline for preventive maintenance across the life of the system.