Final answer:
Check valves prevent reverse flow of gas in an anesthesia machine.
Step-by-step explanation:
The valves in an anesthesia machine that prevent reverse flow of gas or transfer of gas from one high-pressure cylinder to a cylinder of lower pressure are called check valves.
Check valves are one-way valves that allow gas flow in one direction and prevent backflow. They ensure that gas only flows from the high-pressure side to the low-pressure side, maintaining a unidirectional flow within the anesthesia machine.
For example, the check valve located between the oxygen cylinder and the anesthesia circuit prevents any reverse flow of oxygen and ensures that the flow of oxygen is always in the direction from the cylinder to the circuit.