A gallon or more of gasoline was poured down the side of my house. I am assuming it soaked into the basement concrete blocks below ground. I have opened the windows (it is January, very cold). I placed a fan in the window of the room that has the wall where the gas was spilled. It is day three, a lot of the smell is gone, but still enough to make me nauseated and a fierce headache. I read somewhere that it can take months to evaporate out of the concrete. Is this true. And if it is, is there anything I can do to help neutralize the smell? I am desperate. Thanks.