definition
strict definition
air raid shelter
A space specially designed and designated to protect people during bombardment or air raids.
An air-raid shelter is an area dedicated to the protection of persons in the event of any kind of bombardment. Only places which are specially designed and designated for this purpose are classified as air-raid shelters, even if a space is structurally qualified to protect people.
Both protective design and explicit designation are required. A strong basement or other robust space is not enough by physical construction alone.
The use provides refuge for people. An air-defense position intended to engage attacking aircraft has a different function, even when both uses share a site.
