The adverse human health effects due to ionizing radiation are well known. Radon is the major source of background radiation among those that are of natural origin. It contributes about 55% of the natural radiation dose to humans. It is a colorless, odorless, and tasteless radioactive noble gas that comes from the natural radioactive decay series of uranium. Radon can be found everywhere in the atmosphere and become attached to aerosols in the air. The aerosols carrying radon and its progeny can be inhaled and deposited in different regions of the human respiratory tract. The deposited radioactive aerosols continue to decay and exposing the lung to ionizing radiation can destroy sensitive cells in the lung, causing a mutation that turns to be cancerous. Different countries and international and national organizations put their action levels to reduce radon lung cancer risk. The Environmental Protection Agency recommends 148 Bq/m3 as the action level. On the other hand, International Commission for Radiation Protection (ICRP) recommends 200 Bq/m3 as the action level. The main objective of this review is to focus on how radon is established as a health hazard, ways of radon detection and measurements, methods of reducing and controlling high indoor radon concentration, and what are the recommended international action levels of radon concentrations. It mainly focuses on the health perspective of radon studies because it is now a crucial and hot issue in the world. In most developing countries like our country Ethiopia, radon studies are not well investigated.