A door closer is an automated device that closes a door after it has been opened. The device is attached to both the door and door frame, and can be either manual or automatic. It prevents the door from standing open, slamming closed, or pulling open to slam against the wall or door frame in the presence of strong winds. The most common examples can usually be found in schools, convenience stores, and a multitude of other smaller businesses and public buildings.
Manual closers create resistance when the door is opened by making use of the force exerted to compress a spring. When the pressure lifts, the spring releases to close the door. The speed at which the door closes is controlled by the release of pressure in a chamber. A hydraulic chamber releases oil, while a pneumatic closer uses air to offer resistance to the spring.
Some automatic closers are capable of opening a door automatically via remote access control, or through use of motion sensors. The automatic door closer is more commonly known as a door opener due to its combined ability to close and open a door. This device is usually activated by triggering a motion sensor, stepping on a sensor plate, or pressing a button. Many large stores, fast food chains, and businesses make use of this type of door closer to accommodate heavy consumer traffic and to permit convenient access for people with handicaps.
The two main types of door closers can be further categorized by variations in appearance and placement. A surface-mounted door closer is often attached to the top of a door, above the hinges and in the corner. Residential screen and storm doors often place the door closer about halfway down the door's length. Concealed door closers can be hidden in either the door frame or the floor, among other locations.
A door closer can provide significant advantages, including decreasing the amount of wear and abuse a door suffers over time. One safety feature the door closer provides is the controlled motion of the door, which can prevent pets or small children from getting caught or injured by a slamming door. Automatically closing doors can prevent air from entering or escaping, which helps maintain a steady temperature inside a room and cuts down on the cost of heating or cooling. This feature also helps contain outbreaks of fire by cutting flames off from other areas in a building.