Another name is safe room, a room which makes you feel safe in the event of an emergency.

A panic room is constructed of weather-resistant material.

A panic room will contain, among other things, provisions for all the family members, and gas masks for the event of a chemical attack.

They're designed to protect against a variety of disasters -- both natural and man-made -- including hurricanes and tornadoes.

You can use it as a vault for expensive possessions or rare collections.

The best place, especially for safety against hurricanes, is on the ground floor.

It should ideally have an invisible entrance, such as one concealed by a bookcase.

The most common ones are electromagnetic locks, which use magnetic force between the frame and the lock.

Soundproofing means that if you do contact the emergency services in case of invasion, you don't have to worry that the intruders will hear you.

Ventilation is key here. Otherwise, the danger of carbon monoxide poisoning will be a major concern.

You should have sufficient water for all occupants, usually about one gallon (3.78 liters) per person per day.

The architect, as well as the security firm working on your panic room, should sign a confidentiality agreement to keep this room secret.

Depending on its amenities, hi-tech equipment and quality of construction, a panic room could cost between $50,000 and $500,000.

If you want to go ahead and build a panic room, at least make use of what you've got. Try converting a closet or windowless extra room for this purpose.

According to recent estimates, nearly every new mansion in Los Angeles is built with a panic room.

After the Twin Towers attack on September 11, 2001, more and more middle-income families began to invest in panic rooms.

They do so in the case of domestic violence, as a safe area within the victim's own home.

During the times of the feudal lords and castles, they used safe rooms as a defense against intrusion. They were often called the castle keep.

They would hide banned liquor there, away from the eyes of the authorities.

They were storm cellars, like in the movie The Wizard of Oz.