The function of the radiator air vent is to provide a means for air to be driven out of the radiator as steam enters. At a given pressure the fill time of a radiator varies proportional to its heat capacity and inversely proportional to the venting capacity of the radiator air vent. It is possible to control the speed at which a radiator will fill with steam by installing a radiator air vent with a certain venting capacity. Used in this manner, radiator air vents are helpful in evening out the heat distribution in a building.