A fire door release device holds a door open during normal use and lets it close when the fire alarm operates. It is the engineered answer to the wedging problem, and its value depends entirely on the interface between the alarm system and the device, which is the part that is most often installed without being properly commissioned.
How release is triggered
Wired devices are connected to the fire alarm system, either to a dedicated output or to a monitored circuit, and drop the door when the system goes into alarm. They must also release on loss of power, on a fault in the interface, and on the local test button. Acoustically triggered devices contain a sounder detector and release when they hear the alarm signal, which means their siting has to be verified against the actual sound level at the door.
The standard that governs it
The interface between a fire detection system and the equipment it controls is covered by its own British Standard, which sets out the categories of release, the reliability expected and the commissioning required. That standard is what a specifier should be referencing, and it is why hold open devices are not simply an electrical accessory.
Fail safe, and what it means in practice
The door must close on every failure mode, not only on alarm. That includes mains failure, cable damage, panel fault and removal of the device. A device wired so that it holds the door in a fault condition is the opposite of fail safe and is the error to look for when inspecting an existing installation.
Commissioning and testing
Every device has to be proved to release during the alarm test, and that proof has to be recorded per device rather than for the building. Where devices are on a zonal output, a test of one zone does not prove another. Weekly alarm testing is the natural opportunity, and a building that tests its alarm weekly and has never watched the doors is not testing the doors.
Questions people ask about fire door release
Do hold open devices count as maintenance items?
Yes. They are fire safety measures and have to be maintained in efficient working order like any other, which means tested and recorded.
Can a device hold a flat entrance door open?
Flat entrance doors are not normally held open, because the strategy depends on them being shut. Hold open devices belong on common route doors where traffic justifies them.
What happens on a power cut?
The doors close. That is the required behaviour and it is the behaviour to verify, because a building whose doors stay open on power loss has a wiring fault, not a feature.
Is a fire door retainer the same as a hold open device?
The same thing under a different name, and both describe a device that legitimately holds a fire door open and drops it when the alarm sounds. The name matters less than the two properties: it has to release on every failure mode, not only on alarm, which means mains failure, cable damage, panel fault and removal of the device itself; and its release has to be proved during the alarm test and recorded per device. A wedge, a hook and a bin propping the door are none of those things.
Do fire door retainers have to be tested individually?
Yes, and this is the detail most often missed. Proving that a zonal output fired does not prove that every device on it released, because a device can fail while its zone works. The record should name each device, its location and the date it was proved to drop, in the same way a door check record names each door. Where a building has dozens of them, that record is also the only way anybody knows one has been taken off a wall.
What is an emergency door release key, and where is one allowed?
It is the green break glass or key switch unit beside an electrically held door that drops the lock so people can get out when the access control fails or the fire alarm operates. Its place is on the escape side of any door on an escape route that is held by a magnet or an electric lock, and the rule it satisfies is that people must be able to leave without a key at all times. Two things are checked on an audit: that the unit is visible and reachable from the direction of travel, and that operating it actually releases the door, which is a test somebody has to perform rather than assume.