Liquid Oxygen

This system stores oxygen in liquid form. The liquid is kept in large stationary containers called reservoirs or base units. Portable tanks are filled from the reservoir for travel or use outside the home. The liquid turns into gas before it leaves the container and it remains a gas when it is breathed in. Most liquid oxygen setups include a liquid reservoir and a portable unit.
These are examples of liquid reservoirs and portables.

Liquid Helios Liquid Oxygen 21 31 41 Liquid Portable