ResourcesGlossary: the science
Alpha particle
Short answer
An alpha particle is a positively charged particle made of two protons and two neutrons, given off when some radioactive atoms decay. Radon-222 is an alpha emitter.
What alpha particle means
EPA says alpha particles lack the energy to penetrate even the outer layer of skin, so exposure to the outside of the body is not a major concern.
The harm comes from the inside. If alpha emitters are inhaled or swallowed, EPA says, the alpha particles can damage sensitive living tissue.
Counting what an alpha particle carries away
An alpha particle has a mass number of 4: two protons and two neutrons. Each row subtracts or divides by that 4.
| What is counted | The sum | Result |
|---|---|---|
| One alpha particle | 2 protons + 2 neutrons | 4 |
| Radon-222 after giving off one alpha particle | 222 - 4 | 218 |
| From uranium-238 to lead-206, the two ends of EPA's chain | (238 - 206) / 4 | 8 alpha particles' worth of mass |
What it means for your home
This is why radon matters as something you breathe, not something you touch, and why the fix deals with the air indoors.
The method EPA says is primarily used is a vent pipe system and fan, which pulls radon from beneath the house and vents it to the outside.
Where to go next
- Radon level interpreter. Read the level your test found against EPA's guidance.
- How radon causes lung cancer. What happens in the lungs, step by step.