Radiation and Radiological Disasters. According to ICRU Report 51 the dose equivalent, H, is the product of Q and D at a point in tissue, where D is the →absorbed dose and Q is the quality factor at that point, thus: H = Q D. The unit is J kg-1, the special name for the unit of dose equivalent is sievert (Sv). The quantity dose equivalent is defined for routine radiation-protection applications. It should not be used in the numerical assessment of high-level exposure, for example in radiation accidents. In 1991 the International Commission on Radiological Protection introduced for dose limitation proposes a quantity called organ dose equivalent, based on the radiation weighting factor wR and DT,R the mean absorbed dose in a tissue or organ. Accordingly, the organ equivalent dose HT,R in a tissue or organ T by the radiation type R is: HT,R = WR DT,R. In a mixed radiation field the following equation applies for the overall organ equivalent dose HT in a tissue or organ T: HT = ΣRWR DT,R. The unit is joule/kg (J/kg). The special name for the unit of the organ dose is sievert, symbol: Sv. Occasionally the former unit name rem is used. 1 sievert is equal to 100 rem. The quantity organ dose equivalent is only used in radiation protection. These quantity offer a basis for the estimation of →stochastic radiation effects for radiation doses far below the threshold values for →deterministic radiation effects