Door Closers

A door closer is a mechanical device that closes a door, in general after someone opens it, or after it was automatically opened. There are two general styles of door closers: manual and automatic.
A manual door closer stores the energy used in the opening of the door and releases it to close the door.
An automatic door closer (more often called door opener) opens the door itself, typically under the control of a push button, motion detector or other device, and then closes it as well, typically employing a motion or proximity detector to determine when it is safe to close the door.
Door closers are most commonly used on fire doors, which need to be closed in the case of fire to help prevent spread of the fire and smoke.