Gamma-permanent - dose radiation (x-rays in 1 hour), created in the air unfiltered gamma radiation of a point source activity 1 km mkori on distance of 1 sm from it; serves for the specifications of gamma radiation.
Gamma constant radium is 9.3 p/hour. With filters applied value of gamma-constant decreases (with platinum filter thickness of 0.5 mm gamma constant radium - 8,3 R/h). Cm. also Gamma-radiationDose ionizing radiation.