If another person uses your Facebook account without your permission or if you have been using your friend's smart device (computer, smartphone or tablet) to login to your Facebook account and you forgot to logout from that device, then you can easily logout/close that sessions from any other device by following the steps below:
How to logout from any Facebook session and protect your privacy.
Step 1: Login to your Facebook Account
Go to Facebook webpage (http://www.facebook.com) and login to your Facebook account.
Step 2: Open Facebook Active sessions.
2. Inside Account Settings options, choose “Security” on the left pane.
3. In Security options, click to “Edit” option in Active Sessions line.
Inside Facebook Active Sessions you can view some very useful information about your account activity:
a. The device name used for each session (If you have already specified one)
b. The time when each session started.
c. The approximate location for each session (e.g. Athens, GR)
d. The internet browser used for each session (e.g. IE, Mozilla, Chrome)
After doing this, you have successfully closed the unwanted session.
Advice*: If you discover unwanted activity inside “Active Sessions” then – after ending the desired activity- change immediately your Facebook password.