Although radon starts as a gas, it can eventually decay into radioactive radon particles. So how big are these radon particles? It turns out, the size of radon particles can vary depending on what else is in your air.
Radon Particles: Two Sizes
Size #1: Radon Attached to Aerosol Particles (50-300 nanometers)
After decay, radon particles are so small they easily attach to larger aerosol particles. For example, scientists released radon in test chamber along with incense smoke.
The incense particles averaged around 0.1 microns (100 nanometers), so the radioactive particles that had radon attached were also around 0.1 microns.
Then they burned an oil candle, and that created smaller particles. Many of those particles were from 0.06 to 0.10 microns (60-100 nanometers). As a result, the radioactive particles were also smaller.
Size #2: Unattached Radon Particles (.5-3 nanometers)
Radon particles that do not attach to aerosols are free radon atoms and far smaller, ranging in size from .5-3.0 nanometers.
Read More: Do HEPA Filters Remove Radon Particles?