Exit Device Option Overview
This article covers a few of the options available to increase exit device utility in diverse applications. For basic information about exit devices, electric latch retraction or delayed egress, please visit the pages listed above.
To 'dog down' an exit device is to leave it in an unlocked position by using a 'dogging' mechanism in the bar. The dogging mechanism is usually activated by a hex key (allen wrench) inserted through a hole in the push bar. At right is shown an exit device with a dogging mechanism that is activated by a mortise cylinder instead of a hex key. This is said to be an exit device with cylinder dogging. To activate, one pushes the push bar and turns the key one full revolution.
Exit devices can also be ordered 'less dogging', which means they come with no dogging feature. Fire rated exit devices never have a dogging feature.
Less Bottom Rod
Vertical rod exit devices are available less bottom rod for applications where it is desirable not to have a strike on the floor or otherwise desirable not to have a bottom rod or latch. A vertical rod floor strike takes up little space yet could be an obstruction to someone with a walker, for example. In the case of surface vertical rod exit devices, the bottom rod and latch are exposed and subject to impact by utility carts, gurneys, or even mischievous human feet. A less bottom rod surface vertical rod exit device is one way to avoid this problem.
To apply an electric strike to a vertical rod device, it would be necessary to lose the bottom rod and latch. This application is problematic because the 'play' created by losing the bottom rod is compounded by the lack of rigidity in the electric strike. Doors equipped with less bottom rod exit devices and electric strikes tend to feel loose, sloppy and insecure. Also, if the door sags at all over time, people will be able to pull the door open while locked.
Less bottom rod applications are far from ideal, and are usually used only when no other solution will work.
Many fire rated less bottom rod vertical rod exit devices use a device called a "firing pin" or "thermal pin" to secure the bottom half of a door. This pin is a kind of bolt that extends itself from one door into the other door of a pair of doors when the door is heated to a certain temperature during a fire.
Rod and Latch Guards and Bumpers
Available from some exit device manufacturers as an option and also from other hardware manufacturers, such as Rockwood and Don Jo, as an aftermarket add-on, rod and latch guards are used to protect exposed vertical rods and latches from impact. These and other aftermarket manufacturers also make door bumpers to protect the exit device end cap from push-cart impact.
Door bumpers and rod and latch guards can be a real problem solver where exit devices take a beating. If you find that you are replacing vertical rods and latches and/or end caps on a regular basis, you might consider installing these guards.
Tactile warning is an abrasive or milled surface treatment on the touchpad of an exit device. Its purpose is to warn persons with impaired vision that they are entering a hazardous space, such as a stairwell.
Electric dogging is exactly what it says it is. The electric part is accomplished through a solenoid, electric motor, or electromagnet. Some electric dogging does not go into effect until the first person out depresses the touchbar. Other electric dogging is synonymous with electric latch retraction. Find out exactly how a manufacturer's electric dogging works so that you can decide if it matches your application.
Monitor switches are available to monitor when the touchpad is depressed and / or when the latch is or latches are retracted. These switches are used to communicate with electrical devices outside the exit device such as a relay, alarm panel, or access control system. Usually they are micro switches with little current capacity - in the range of around 200mA - so if, for example, one wanted to use one to deactivate an electromagnetic lock, one would use a relay rather than trying to run say, 450mA at 24vdc for a Schlage Electronics 390 electromagnetic lock through the monitor switch on the exit device.
A relative newcomer to the world of exit device options, antimicrobial finish is available on exit device touchpads to inhibit the spread of germs.
Exit devices are available with battery operated self contained alarm function. Typically they are equipped with a key switch (requiring a mortise cylinder) that arms and disarms the alarm and provides timed bypass.
Lighted or Luminous Touchpad
Lighted or luminous touchpad signage is available on many exit devices. Since in a fire the electricity is very likely to be shut off, these lighted touchpads help people find the exit safely in panic situations in the dark.
On wood doors or in fire door applications, through-bolts help secure an exit device to the door. In some instances, through-bolting is mandatory to comply with UL specifications.
Electrified Outside Trim
Electrified outside trim allows remote locking and unlocking of the outside trim to provide access control. Because current draw is so much lower in many cases than electric latch retraction, electrified trim is often a good choice. However, electric latch retraction or an electric strike must be used if the purpose of the electric unlocking to allow a power operator to open the door.
Fail safe electrified outside trim is a very good choice for stairwell doors which must remain postively latched, but unlocked, in the event of a fire.
Hurricane rated exit devices have superior holding capabilities to remain latched in high winds. They are equipped with heavier latches and strikes.
Pneumatic Latch Retraction
Pneumatic latch retraction is used instead of electric latch retraction for access control in explosive environments where electric spark would be an extreme hazard. Instead of a solenoid to retract the latches, these devices are equipped with a pneumatic piston. Pnuematic exit devices require an air compressor.
Vertical Rod Device with Pullman Latches
Pullman latches are simple spring-loaded latches that spring out every time they are not retracted. Standard vertical rod exit device latches have a release mechanism that causes them to stay retracted until the door closes. The usual reason to use a pullman latch is if you want to install a vertical rod device less bottom road and install an electric strike in the header to release it electrically. See above, the "less bottom rod" section.