How does a door closer work?

During an average day, almost everybody comes in contact with a wide variety of door closers, both automatic and manual in nature. Door closers are used in everything from the screen door at the front of your house to the front door of your workplace.

In fact, door closers can be found in one way or another in just about every commercial building. They are a requirement for fire doors. The reason for this is that fire doors must remain closed at all times when they are not in use, and by including a manual door closer, this ensures that the door stays closed.

The first door closer was a simple spring. One end of the spring was attached to an anchor point on the door frame and the other end was attached to the door. These springs were fairly effective, but they had the obvious problem of slamming the door closed when the spring contracted to its resting position. It also made it difficult to close a door containing glass without breaking it.

The replacement for simple spring door closers became the pneumatic system door closer. This is the current standard for screen and glass doors for homes. The pneumatic system door closer works by an internal piston drawing air into the chamber while compressing an internal spring when the door is opened, and then slowly leaking the air out of the chamber as the spring pushes the piston back, closing the door. A similar system is used in the commercial door versions with the main difference being that many commercial door closers use a hydraulic damper. This is a fluid-filled chamber that gradually releases the pressure to close the door more slowly.

Electric door closers, also known as automatic door closers, use motors to control the opening and closing of doors. They are triggered from a variety of mechanisms, the most common of which is a motion or proximity sensor. This sensor detects motion within a designated area and opens the door. The sensor stays active until the person leaves the designated area before closing the door. Another common mechanism is the push button, seen mostly on or around doors designed for the disabled. The door runs on a track installed into the door frame and is controlled by a drive motor that is programmed to open and close the door at a specific speed that meets the requirements of the Power Operated Pedestrian Door Standard, a rule developed by hardware manufacturers in coordination with the American National Standards Institute (ANSI).