| Half-life: The time during which one-half of a given quantity of a radionuclide undergoes radioactive decay into another nuclear form. A half-life can last from millionths of a second to billions of years. Half-thickness: The thickness of a slab material that reduces by half the intensity of radiation incident on one side of the slab. HAZ-MAT Training: Hazardous Materials training required for all individuals preparing or transporting gauges. Initial training is covered in the Gauge Safety Certification class and must be renewed every three years. APNGA promotes and recommends renewal every year. Health Physics: A interdisciplinary science that includes elements of physics, biology, chemistry, statistics and electronic instrumentation focusing on providing information used to protect individuals from the effects of ionizing radiation. Helium-3 Detector Tube: A helium-3 gas filled tube used to measure thermalized neutrons. Used in a gauge to determine moisture content. | 
