This would convert to a 1,000 rad exposure for two minutes spent inside the building. The radiation dose at which half the exposed group of people would be expected to die, i.e. the 50 percent lethal dose, is 250 rad. Between 250 and 1,000 rad, death is usually due to gross damage to the stomach and gut. Below 250 rad death is principally due to gross damage to the bone marrow and blood vessels. Penetrating radiation in doses above 100 rad inflicts severe skin burns.
Lower doses produce burns in some people.
Vomiting and diarrhoea are caused by doses above about 50 rad. There are some individuals who are more sensitive to radiation, however, showing typical vomiting and diarrhoea radiation sickness patterns with doses as low as 5 rad. An individual may react differently at different times of life or under different circumstances. Below 30 rad, for most individuals, the effects from external penetrating radiation are not immediately felt. By sharpening our perceptions more subtle radiation effects can often become observable where once they went unnoticed.