What are they?
These shelters can be most effective when on the middle floors of some tall buildings or parking structures, or below ground level in most buildings with more than 10 floors.
People were alerted with sirens set up by the Emergency Broadcast System.
People were instructed to stay in for 2 weeks. When finally coming out, don't just come out and resume life, but start off by coming outside for an hour. Then work your way up.
Idealized American fallout shelter circa 1957.
A basic fallout shelter consists of shields that reduce gamma ray exposure by a factor of 1000.
A sign pointing to an old fallout shelter in New York City.
Fallout shelters were (and still are) everywhere.
Here is an image of "Fat Man"
This is one of the nuclear weapons that fallout shelters were aiming to protect from.