1.   As the hot steam enters these chambers, it meets the cool water, quickly condenses and creates a vacuum.

2.   A radiator that is perfectly level or pitched away from the intake valve will trap water so steam cannot enter.

3.   A partly opened valve will allow the steam to enter, but it will also trap the condensed water and create a water hammer.

4.   Each radiator is equipped with an air valve mounted on the side, that allows the cool air trapped in the radiator to escape so the steam can enter.

5.   It allows air to escape from the radiator so steam can enter.