Radon is an invisible gas formed in the Earth’s crust. It surrounds every one of us as part of the air we breathe.

Radon comes from the rocks and soil beneath our buildings. This substrate contains traces of uranium. Over time, the uranium breaks down and forms other elements. This is called radioactive decay. Radon is one element in the decay chain of uranium. When radon gas decays, it emits radiation in the form of an alpha particle. This radioactive particle is made up of two protons and two neutrons.

Airthings sensors monitors radon by sensing what are called alpha particles. Alpha particles are emitted as by the radioactive gas radon, and the Airthings device has a sensor calibrated to detect alpha particles.

This sensor, called a photodiode, is the digital version of film, creating a “radon picture” from how many particles impact the sensor. But you can’t just have any old photodiode in a detector and accurately gauge radon levels. There are many different particles that could “trigger” the sensor, so it must be specially designed to only register relevant particles. To rule out irrelevant particle impressions, the Airthings team developed a proprietary algorithm that allows the device to be sensitive to radon but not other particle “noise.”

Radon levels change over time. That’s why it’s so important to measure continuously, to ensure your levels stay low.

The amount of radon emitted from the ground and the amount that actually enters our home can change due to the following reasons: