Editing Fallout shelter (section)

== Different types of radiation emitted by fallout ==

=== Alpha (α) ===
In the vast majority of accidents, and in all [[atomic bomb]] blasts, the threat due to beta and gamma emitters is greater than that posed by the alpha emitters in the fallout. Alpha particles are identical to a helium-4 nucleus (two protons and two neutrons), and travel at speeds in excess of 5% of the speed of light. [[Alpha particle]]s have little penetrating power; most cannot penetrate through human skin. Avoiding direct exposure with fallout particles will prevent injury from alpha radiation.<ref name=NWSSC>{{cite book|last=Kearny|first=Cresson H|title=Nuclear War Survival Skills|year=1986|publisher=Oak Ridge National Laboratory|location=Oak Ridge, TN|isbn=0-942487-01-X|pages=45|url=http://www.oism.org/nwss/s73p916.htm}}</ref>

=== Beta (β) ===
[[Beta particle|Beta radiation]] consists of particles (high-speed electrons) given off by some fallout. Most beta particles cannot penetrate more than about {{convert|3|m|ft|0}} of air or about {{convert|1/8|in|mm|0|order=flip|abbr=on}} of water, wood, or human body tissue; or a sheet of aluminum foil. Avoiding direct exposure with fallout particles will prevent most injuries from beta radiation.<ref name=NWSSD/>

The primary dangers associated with beta radiation are internal exposure from ingested fallout particles and beta burns from fallout particles no more than a few days old. [[Beta burn]]s can result from contact with highly radioactive particles on bare skin; ordinary clothing separating fresh fallout particles from the skin can provide significant shielding.<ref name=NWSSD>{{cite book |last=Kearny |first=Cresson H |title=Nuclear War Survival Skills |year=1986 |publisher=Oak Ridge National Laboratory |location=Oak Ridge, TN |isbn=0-942487-01-X |page=44 |url=http://www.oism.org/nwss/s73p916.htm}}</ref>

=== Gamma (γ) ===
[[Gamma ray|Gamma radiation]] penetrates further through matter than alpha or beta radiation. Most of the design of a typical fallout shelter is intended to protect against gamma [[electromagnetic radiation|rays]]. Gamma rays are better absorbed by materials with high atomic numbers and high density, although neither effect is important compared to the total mass per area in the path of the gamma ray. Thus, lead is only modestly better as a gamma shield than an equal mass of another shielding material such as aluminum, concrete, water or soil.

Some gamma radiation from fallout will penetrate into even the best shelters. However, the radiation dose received while inside a shelter can be significantly reduced with proper shielding. Ten halving thicknesses of a given material can reduce gamma exposure to less than {{frac|1|1000}} of unshielded exposure.<ref name=NWSSE>{{cite book |last=Kearny |first=Cresson H |title=Nuclear War Survival Skills |year=1986 |publisher=Oak Ridge National Laboratory |location=Oak Ridge, TN |isbn=0-942487-01-X |pages=11–20 |url=http://www.oism.org/nwss/s73p912.htm}}</ref>