| Door closers are a common sight in most commercial | | | | mechanism is only visible when the door is open. Once |
| buildings. They are mechanical devices typically installed | | | | it closes, a jamb-mounted device is invisible on both the |
| to ensure that doors get closed after patrons, | | | | interior and exterior side. |
| residents and other building-users open them. | | | | Manual door closers (whether overhead or |
| Local building codes usually determine what exits must | | | | jamb-mounted) work on the principle of pneumatics (air |
| be outfitted with door closers. Some may require all | | | | pressure) and stored energy. The device stores the |
| doors have them. At the very least, most regions | | | | energy that is generated when someone pushes the |
| require them on fire doors. The reason for this is that | | | | door open. It then uses this energy to close it without |
| fire doors are to remain closed at all times when not in | | | | any additional human force being applied. |
| immediate use. This helps to ensure that, should a fire | | | | Closing speed can be controlled and adjusted as |
| break out in the building, flames do not spread from | | | | desired. Some use hydraulic dampers (these are most |
| one part of the building to another before firefighters | | | | common,) others employ spring mechanisms. Sets of |
| can bring the blaze under control. | | | | screws are adjusted to achieve desired closing and |
| Door closers are either surface mounted or concealed, | | | | latching speed. (Many regions have building codes |
| and are so-named due to how they are installed on | | | | which mandate closing speed on door closers, usually |
| (surface mounted) or within (concealed) the door. | | | | in deference to disabled patrons who may take longer |
| Surface-mounted devices appear as a small box | | | | to enter and exit.) |
| attached to the top corner of the door. A jointed "arm" | | | | Automatic door closers, as the name suggests, use |
| extends from the top of the box to the frame where | | | | electrical power instead of stored energy. This style is |
| it is bolted in. A concealed device is mounted within the | | | | less common, due to the amount of power required |
| material of the door itself, meaning that the only part | | | | and the interest of economy and conservation. |
| visible to the eye is the arm. | | | | Automatic devices are typically found on buildings |
| Door closers come in two major types: manual and | | | | where particular entrances/exits are highly controlled |
| automatic. The most common is the manual type. | | | | and monitored and buzz-in/out is employed, such as |
| Over seventy percent of those found in commercial | | | | residential care homes. |
| buildings in North America are this type. | | | | Door closers that are intended for use on fire doors |
| Additionally, manual door closers may be overhead or | | | | must be fire-rated. Devices that are fire rated have |
| jamb mounted. The overhead style is more common, | | | | been tested by a recognized testing facility to ensure |
| particularly on older public buildings. This type looks like | | | | that they can withstand heat/flames. They must be |
| the typical box and arm device. | | | | able to hold fire at bay for as long as the fire door |
| A jamb-mounted device is installed on the inner frame | | | | itself does; a typical one is usually required by law to |
| of the door and the inside edge of the door. The | | | | contain fire/flames for a minimum of three hours. |