(rad) One rad is the absorbed radiation dose of 100 ergs of energy by one gram or 0.01 joules of energy by one kilogram of matter. In the SI system of units, the rad is replaced by the gray (Gy). 1 Gy = 100 rad. See also Absorbed Dose Rate.

A radiation meter is used to measure radioactivity.
Beta emitting isotopes, such as C-14, P-32, P-33, and S-35, are best detected with a Geiger-Mueller counter (GM).
Gamma emitting isotopes, such as I-125, I-123, I-131, and Tc-99m are easily detected with a gamma meter equipped with a sodium iodide (NaI) probe.
An isotope that cannot be detected with most survey meters, unless present in large activities, is tritium (H-3). Tritium emits beta particles with energies insufficient to enter the sensitive volume of most detectors.

Radiation safety concerns the safe use of ionizing radiation. The radiation exposure has to be controlled to protect people and the environment from unnecessary exposure and the damaging effect to the health. Legal regulations require that radiation exposure (individual radiation exposure as well as collective dose) must be kept as low as reasonably achievable.
The electromagnetic spectrum includes x-rays, gamma rays, ultraviolet radiation, visible light, infrared radiation, and radio waves. Additionally, there are several types of particulate radiation e.g., alpha and beta particles. All types of radiation are used in a wide range of medicine, industry, research and communication. Radiation risks can occur due to either long-term low level exposure or short-term high level exposure. A well-functioning dosimetry program is essential for a safe use and for compliance with federal and state regulations.

Three basic rules have to be observed for a safe use of ionizing radiation.

See also Inverse Square Law, Administrative Dose Guidelines and Annual Dose Limit.

Radiation shielding is the process of limiting the penetration of radiation into the environment, by blocking with a barrier made of impermeable material. This protective barrier is usually formed of a material with high density, for example lead that absorbs the radiation.
Radiation sources are self-shielded with absorbing material incorporated into the equipment, adjacent to the source to reduce stray radiation to the surrounding area below dose limits.
Rooms with x-ray or other radiation equipment are additionally shielded with lead-lined walls to reduce the radiation exposure to humans within the facility. The amount of shielding required to protect against different kinds of radiation depends on how much energy they have. The shielding calculations are based on the half value layer of the primary radiation beam. Sufficient half value layers of shielding are calculated to reduce the radiation exposure outside the room to reasonable levels.
Personal shielding requirements depending on the type of radiation:
See also Radiation Safety.

Radiation worker are staff or students whose work necessitates the operation of any irradiating apparatus, or involve the handling of radioactive material.