Radiation is the emission and propagation of energy in the form of waves, rays and particles. Gamma rays (ionized radiation) have high energy and low-wavelength radiation. It has an energy range from a few kilo-electron volts (keV) to a few mega-electron volts (MeV). Gamma rays are capable of penetrating the tissues and cells of the human body due to their high energy and can be considered biologically hazardous and can damage internal organs, tissues and bone marrow. When the gamma emission process occurs, the resulting atoms are unchanged in atomic number and mass terms. Many isotopes are available that emit gamma radiation and are used for treatment in the medical field. The released gamma rays have a distinct energy level. Alpha and beta decay produce daughter nuclides in an excited state, and consequently, during de-excitation, they emit gamma rays. Generally, this de-excitation occurs in a very short period of time (a few femtoseconds). Gamma rays are also emitted by many nuclear reactions through radionuclides such as 60Co, 137Cs, 252Cf, 244Cm, and 238U. Humans are continuously exposed to gamma radiation, whether inside or outside of their houses, due to the atmosphere and other natural activities. In fact, the gamma radiation level inside the house is greater than that outside the house. The health impact of exposure to radiation via inhalation within the indoor environment is a major public concern worldwide. The worldwide average outdoor dose rate is 59 nGy/h, and the indoor absorbed dose rate in air is 84 nGy/h. The indoor to outdoor ratios varied from 0.6 to 2.3, with a world population-weighted average value of 1.4.