By Loek Essers
@loekessers
During a major disaster, Facebook users can let their friends and family know they are 
safe by using the new Safety Check tool.
When the tool is activated and Facebook determines that a user may be in an area where a natural disaster occurred, the social network will send a notification asking if the user is safe. If the response “I’m Safe” is selected, Facebook will create a post and share it on the user’s news feed, telling friends they are out of peril. Friends too have the possibility to mark someone as safe.
Facebook determines a user’s location by looking at the city listed in their profile, their last location if they’ve opted in to the Nearby Friends service, and the city where they are using the Internet, presumably derived from their IP address. If the location is wrong the user can tell Safety Check they are not in the affected area.
If your friend is in a disaster area and the tool has been activated, you will receive a notification about those friends that have marked themselves as safe. Clicking on the notification will show a list of their updates.
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