The alpha particle can penetrate through small distances and up to a certain range and penetrate the materials.
The alpha particles are mainly used (in very small amounts) in materials such as smoke detectors.
Also, alpha particles have a very less ability to penetrate other materials.
In other words, these particles of ionizing radiation can be blocked by a sheet of paper, skin, or even a few inches of air.
They are relatively heavy, and only travel about an inch in air.
Alpha particles can easily be protected by a single sheet of paper and cannot penetrate the outer dead layer of skin, so they pose no danger when their source is outside the human body.
