Alpha radiation is a heavy, very short-range particle and is actually an ejected helium nucleus. Some characteristics of alpha radiation are:

• Most alpha radiation is not able to penetrate human skin.
• Alpha-emitting materials can be harmful to humans if the materials are inhaled, swallowed, or absorbed through open wounds.
• A variety of instruments has been designed to measure alpha radiation. Special training in the use of these instruments is essential for making accurate measurements.
• A thin-window Geiger-Mueller (GM) probe can detect the presence of alpha radiation.
• Instruments cannot detect alpha radiation through even a thin layer of water, dust, paper, or other material, because alpha radiation is not penetrating.
• Alpha radiation travels only a short distance (a few inches) in the air but is not an external hazard.
• Alpha radiation is not able to penetrate clothing.

Examples of some alpha emitters: are radium, radon, uranium, and thorium.

Beta radiation is a light, short-range particle and is actually an ejected electron. Some characteristics of beta radiation are:

• Beta radiation may travel several feet in the air and is moderately penetrating.
• Beta radiation can penetrate human skin to the “germinal layer,” where new skin cells are produced. If high levels of beta-emitting contaminants are allowed to remain on the skin for a prolonged period of time, they may cause skin injury.
• Beta-emitting contaminants may be harmful if deposited internally.
• Most beta emitters can be detected with a survey instrument and a thin-window GM probe (e.g., “pancake” type). Some beta emitters, however, produce very low-energy, poorly penetrating radiation that may be difficult or impossible to detect. Examples of these difficult-to-detect beta emitters are hydrogen-3 (tritium), carbon-14, and sulfur-35.
• Clothing provides some protection against beta radiation.

Examples of some pure beta emitters: strontium-90, carbon-14, tritium, and sulfur-35.

The emission of a neutron from the nucleus of an atom

• usually emitted as a result of spontaneous or induced nuclear fission.
• Able to travel hundreds or even thousands of meters in the air, they are however able to be effectively stopped if blocked by a hydrogen-rich material, such as concrete or water.
• Not typically able to ionize an atom directly due to their lack of a charge, neutrons most commonly are indirectly ionizing, in that they are absorbed into a stable atom, thereby making it unstable and more likely to emit off ionizing radiation of another type.
• Neutrons are, in fact, the only type of radiation that is able to turn other materials radioactive.