In an emergency, where hazardous materials may have been released into the atmosphere, authorities may issue a shelter-in-place. This means that residents are asked to go indoors, into a small interior room of their home, with few or no windows, and remain there until the advisory is lifted. (Go HERE for specific shelter-in-place instructions.)
A shelter-in-place was issued in Texas City in the wee hours of Tuesday morning because four refineries and chemical plants lost power Monday evening and early Tuesday morning. School has also been cancelled.