A tire changer does not have to have a bead blaster but it is needed if you want to use it for tubeless tires. A bead blaster sends a large volume air that is under pressure into the cavity of the tubeless tire. This helps to separate the tire from the wheel by breaking the beads. Tubeless tires have very stiff sidewalls and the beads of these tires will not break if you just pump air in at the valve stem.
Compressed air is usually stored externally and is controlled via a foot pedal. First, a hose is attached to the valve stem. Then you press the pedal and compressed air flows into the tire. When the pedal is all the way down, a lot of air is forced into the tire. The blast of air may be combined with additional air entering through holes in the tire changer base. The combination of valve stem air and air from the bead blaster is enough to break the beads.
When a blast of air is applied to the top sidewall it removes the top bead of the tire to the rim. Then the air is directed at the bottom sidewall so the lower bead is broken. The process is very quick – it takes just a second. Thanks to the continual pressure from the valve stem, the beads are forced permanently out of position.