Ionizing radiation members, to comply with a European Directive. The FAA has a recommended limit of 1 mSv total for a pregnancy, and no more than 0.5 mSv per month. Information originally based on "Fundamentals of Aerospace Medicine" published in 2008. Hazardous levels of ionizing radiation are signified by the trefoil sign on a yellow background. These are usually posted at the boundary of a radiation controlled area or in any place where radiation levels are significantly above background due to human intervention. The red ionizing radiation warning symbol (ISO 21482) was launched in 2007, and is intended for IAEA Category 1,
Radiation exposure into account the absorption characteristic of the target material. Dose is the measure of energy per unit mass deposited by ionizing radiation. For a given radiation field, the absorbed dose will depend on the type of matter which absorbs the radiation. For instance, for an exposure of 1 roentgen by gamma rays with an energy of 1 MeV, the dose in air will be 0.877 rad, the dose in water will be 0.975 rad, the dose in silicon will be 0.877 rad, and the dose in averaged human tissue will be 1 rad. A table giving the exposure to dose