Deadly PushbuttonsBy Brian Rhodes, Published May 15, 2013, 08:00pm EDT
A simple and common misunderstanding in specifying pushbuttons can kill people trying to escape burning buildings. Furthermore, determining buttons that are 'safe' versus 'deadly' can be difficult to detect unless you check how they are implemented. We explain this issue and options to resolve inside.
RTE by the Books
Most Electronic Access Control systems must comply with national/ international code books. We examine the subject in our "Request to Exit Tutorial", a helpful primer on the subject. Perhaps the broadest authority is the IBC (International Building Code) part 1008.1.4.4 that affirms:
"A manual unlocking device (push button) shall result in direct interruption of power to the lock – independent of the access control system electronics. When the push button is actuated, the doors must remain unlocked for 30 seconds minimum. The push button must include signage stating “Push to Exit” and must be located 40” to 48” vertically above the floor and within 5’ of the doors. Ready access must be provided to the push button."
Notice among the key requirements are two key elements:
- Direct interruption: The RTE pushbutton cannot be wired as an input into the door controller, but MUST break power to the lock when depressed (typically maglocks).
- 30 Seconds: The length of time contacts must be MUST be 30 seconds.
Failing to conform with these two items can result in trapping people trying to escape in a emergency.
The Right Pushbutton
In the example door below, the access control installer is using maglocks to secure a busy perimeter opening. The customer asked the installer to use some extra 'Push to Open' pushbuttons instead of agreeing to buy the proposed RTE buttons as part of the access system. Not wanting to lose the sale over an inexpensive component, the installer agreed to use the extras in place of RTE pushbuttons, and considering the button language is very close to what normally is printed on RTE, the installer felt confident in the slight change.
The installer wired the button to interrupt power to the maglocks, and testing the button showed it did in fact drop power to the maglocks as required by code.
However, this installation missed a key point of the code: the latching delay, or timer function of the button. Why is this function so critical?
Timing is Everything
In the example above, the maglock loses power as soon as the button is pushed. However, as soon as the button is released, power is returned to the maglock, relocking the door. Consider that even in a panic situation, it would take several seconds between pushing the button and reaching the unlocked door, and left 'as-is', the door could become a grim example of how escapees are trampled or trapped as they hurriedly rush a locked emergency opening.
The key feature that is missing is a timed 'open' feature of the contacts. A proper RTE pushbutton would include a mechanical or electric timer that would continue to drop power to maglocks for a certain length of time, typically 30 seconds. This allows adequate travel time between pushing the button and passing through the door in an emergency.
Not All 'RTE Labeled' Buttons Timed
The mythical situation above would not pass code for a variety of reasons; including the fact that an ADA wheelchair "door open" button cannot be substituted for RTE Pushbuttons based on verbiage and visibility, aside from function. Those buttons are used to activate automatic door openers and would not likey be used in conjunction with maglocked doors to begin with.
However, finding untimed RTE buttons is common in the mass market. These buttons are useful when combined with external timers or other building management systems where a momentary contact is required to release door locks. Although if improperly installed, these buttons have the same illegal function as the ADA pushbutton, and using them often requires additional equipment or local AHJ exceptions to the IBC code in order to be used.
Two Forms of Timed Button
For Electronic Access Control, RTE buttons with an integrated timer typically takes one of two types:
- Electric: This type of button features a low-voltage or battery powered electronic logic timer that ensures a configured period expires before restoring power to locks.
- Pneumatic: These button feature a plunger and an air-powered piston that retracts at a slow interval. The RTE buttons require no outside power source or air supply for function, and generally are configurable for the same periods as the electric versions.
In either case, the button is not intended to be wired as an input into a door controller to use the access control system to break contact for 30 seconds. The RTE buttons must be directly installed to the lock, so that a malfunctioning system cannot potentially cause harm. The button must be installed as if it worked to physically sever power to the lock under any circumstance.
Murky Codes, Cloudier AHJs
While the IBC Code is very clear on the installation and function of these buttons, many local exemptions that override the IBC are not as well defined. Commonly, local code exceptions are ratified to clarify superficial requirements (ie: instead of green "Push to Exit", buttons must be red, lit, and bi-lingual "EXIT/SALIDA" buttons) but they fail to address the critical timed portion of the IBC requirement.
Due to an impartial understanding of this feature and why it is so important, many AHJs might unwittingly accept half-measure substitutes. Because local codes often do not describe devices well enough, it is incumbent on Access Control designers and installers to prevent a tragedy before it happens.
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