Radon monitoring is essential for controlling a healthy indoor environment in buildings. Radon is a gas that has no color, taste, or smell, yet it is highly carcinogenic. It is heavier than air, which is why it stays close to the ground; however, due to the so-called chimney effect, it can enter buildings through various leaks or cracks. The Czech Republic is among the countries with the highest occurrence of radon in the world. Radon is formed by the gradual decay of uranium and radium, is highly radioactive, and when inhaled over a long period, it settles in the respiratory tract and irradiates it, thereby increasing the risk of lung cancer.