The design is such that a person with normal mechanical skills can construct and operate one.
It is usually human-powered and designed to be employed during a time of crisis.
It was designed to be used in a fallout shelter, but can be used in any situation where emergency ventilation is needed, as after a hurricane.
[1] It was developed from research performed at Oak Ridge National Laboratory by Cresson Kearny and published in Nuclear War Survival Skills.
[2] The basic principle is to create a flat surface with vanes that close when moving air and open when going back to the starting position.