like i said fallout doesnt bind with oxygen. Think of it more as snow. If you close your door snow wont come into your house but some air will. The raditation that your walls dont block will penetrate right though your skin and sure doesnt need you to breath it in. A breathing mask alone will do absolutely nothing for you unless you have a complete raditation exposure suit. Like dixie duke correctly said radiation is reduced very quickly. A week and you will be able to spend some time outdoors and after a month you can about go back to your normal routine. Very few people that arent at ground zero or arent caught outside will die. Long term effects of radiation exposure even small amounts arent really known. thats where iodine comes in. It doesnt block radiation to your body it blocks it only to your tyroid gland. Studies have shown that tyroid cancer is really a problem 10 years or so down the road. What really amazes me is the ammount of people that are ignorant to the dangers. Its not there fault. Back when i was a kid they taught it in school and also taught people what to do. After the cold war was over it was all forgotten. These days with Korea, Iran, Iraq, Libia and just nut cases that can make a bomb theres probably been no time in history where a possiblity of attach is more prevelent. Its time our goverment stepped up and educated people who wont take it on there own to find out the truths.