Mantraps: One Door at a Time

Jan. 4, 2023
Lots of pieces go into building this high-security puzzle.

Mantraps are a high-security solution. In its most basic form, a mantrap is an area that has an entry door on one wall and an exit door on another. There are no other means of entering or leaving the defined area, and only one door can be unlocked and opened at a time. However, mantraps can be designed to involve as many doors as the application requires. Mantraps also can control vehicle entry.

Some types of mantraps include:

  • Secure entry and free egress
  • Restricted entry and exit
  • Normally unlocked (air lock control)

Designing and executing a mantrap involves many pieces that must be put together correctly, including knowledge of life-safety codes.

Mantrap Components

The primary physical parts of a mantrap are doors (or gates), the logic controller, electric locking devices, power, auxiliary control and signaling devices, and the vestibule, or the area that separates the doors in a mantrap.

The doors and vestibules must comply with the appropriate codes, but there’s no standard mantrap design. The “theory of operation,” or how the mantrap works, will be based on a particular site’s requirements. 

Mantraps use electrically actuated locks to control whether a door can be opened. As an alternative, the locks can be augmented with separate electrically actuated devices, such as maglocks or electromechanical bolts. Using separately controlled locks allows the use of existing door locks or opens up the possibilities of enhanced access control and user authentication.

Because mantraps are part of a physical security-management system, unlocking one or both doors typically requires authentication — the possession of a key, knowledge of a passcode, a valid biometric or a combination of these. Some mantraps are staffed, in which case unlocking the doors also might be augmented by visual recognition or some other criteria. Modern designs might incorporate intercoms and video surveillance.

Mantrap Applications

A typical lobby vestibule is designed like a mantrap but not necessarily designed to have mantrap functionality. Lobbies in commercial buildings more often act as air locks to prevent the escape of air-conditioned air.

Bank lobbies might be used to monitor and control who enters, selectively admitting clients, perhaps through electronic access control on the inner lobby door. An exterior door might remain unlocked in a retail bank lobby that has an ATM.

Many schools elect to screen individuals before allowing them inside. IN this case, all perimeter doors remain locked. Visitors are directed to the main entry, where they can undergo the authentication and safety regimen.

Retail establishments, such as high-end jewelry stores, use mantraps to prevent shoplifting.

Other applications include prisoner control, medical isolation and weapon screening.

Earlier in my career, I was involved in designing and supplying security for the military, airlines, the U.S. Department of State and NATO.  One interesting project was setting up mantraps for strategic NATO facilities that were sealed from radio frequency (RF) waves. They were designed to be attack- and explosion-resistant and impervious to passing cryptographic RF snooping. We used keypad door lock controllers to lock and unlock the doors to the sealed vestibules. Obviously, if both doors of the mantrap were ajar at the same time, it would be a security breach.

Mantraps vs. Interlocks

Although the terms tend to be used interchangeably, there are differences between a mantrap and an interlock system.

Interlock simply refers to when the EAC is configured to have an interdependency, which means that the system is locked electrically locked into a certain state until something changes. A mantrap is actually a type of interlock system. Other interlocks commonly are found in facilities that have shared restrooms.

A good introduction to the differences between mantraps and interlocks can be seen in the following example. Imagine a simple two-door mantrap that has the doors on opposite walls. In this system, the card reader on door B wouldn’t be able to function until door A was shut. 

Now consider an interlock system for a bathroom. (See diagram.) In this case, we have a normally locked restroom door, and an outside LED shows green to indicate a free room.

The user presses an outside “push to open” button to unlock the door and enter the bathroom. After they’re inside, the user presses a “push to lock” button. This does two things:

  • The electric strike on the opening will be latched so it can’t be released by using the outside push-button.
  • The LED on the outside will show red.

Upon exit, the user uses the free egress handle on the mortise lock or presses the “push to exit button” on the inside to release the strike. After the door opens, the door-position switch resets the system, which means the outside push-button will function for the next user and the LED resets back to green.

Installation Considerations

Clients often have a vague idea of what they want in terms of a mantrap or interlock, based on something they read, saw or heard, without fully understanding what they’re asking for. When you’re approaching a mantrap project, you must analyze the complete project — the “theory of operation” — how it will operate, and what it will and won’t do. 

Factors to consider:

  • The location of the mantrap
  • Code compliance
  • The means of egress, or the path to leave a space or building
  • Building occupancy 
  • Safety, privacy and security issues

In most cases, life safety is the top priority, because you can’t trap someone in a mantrap. Where patients or inmates are being controlled, they must be confined and controlled for their own protection as well as the well-being of the public. Also, for interlocks that are in restrooms, privacy must be assured.

Because mantraps often are used to deal with drugs, weapons, contraband and individuals who have mental-health issues, rugged locking hardware is required.

Code Compliance

Most buildings are subject to the local building codes and the requirements set forth in the Americans with Disabilities Act (ADA). ADA has specific requirements with respect to maneuverability in vestibules, the manner in which locks are actuated, the amount of pressure required to open a door and the speed and force of a closing door. 

 ADA states:

 4.13.7 Two Doors in Series. The minimum space between two hinged or pivoted doors in series shall be 48 inches plus the width of any door swinging into the space. Doors in series shall swing either in the same direction or away from the space between the doors.

 4.13.5 Clear Width. Doorways shall have a minimum clear opening of 32 inches with the door open 90 degrees, measured between the face of the door and the opposite stop.

As long as the doors comply with ADA and the space between the two doors meets ADA requirements, a mantrap system should be compliant.

Meanwhile, fire codes require an emergency exit path out of all occupied rooms. If there isn’t an emergency exit door out of the secured area, then the mantrap door hardware has to include approved free-exiting devices that override the mantrap controls.

If the mantrap involves the means of egress, your mantrap might have to comply with the same rules that apply to special locking arrangements, such as those for delayed egress.

Some facilities aren’t subject to what normally would be required by the building code — federal facilities, for example. It’s the responsibility of the installer to determine the correct rules for the facility before they deploy lock and security equipment. 

Build or Buy?

Mantrap kits are available. The required components are provided, which will operate according to the desired theory of operation. These kits will streamline your installation.

Maybe your design is unique and isn’t available “off the shelf.” Besides the aspects of proper operation, all components must conform to electrical code. Components that aren’t contained in secure cabinets might be subject to tampering and unintentional damage. If the system design elements aren’t documented clearly, the system can’t be serviced efficiently if a problem were to develop. For a specialized type of system, such as a mantrap, priority service is essential.

I always recommend audio-visual enhancements to provide audible and visual signals to better assure the proper and safe operation of a mantrap, for the clients who use it and the facility staff who manage the system.

Determine what assets exist on-site that can be incorporated into the design and which assets on-site MUST be incorporated. For example, maglocks are incredibly useful for some — but not all — applications. Maglock deployment is bridled by a host of hardware and life-safety requirements that might be avoided by using electric strikes and electrified levers.

Following are several potential components for a mantrap or interlock system.


Altronix offers a wide selection of power supplies, relays and PoE, Ethernet and network hardware that can be used in mantrap applications.

For example, the ACMS12 is a sub-assembly module used in wall- and rack-mount enclosures. Its dual-input design allows power to be steered from two independent low-voltage 5–24 VDC power sources into 12 independently controlled fuse-protected outputs. The ACMS12 routes power to a variety of access control hardware devices, including maglocks, electric strikes and magnetic door holders. Outputs will operate in fail-safe or fail-secure modes. 

The FACP interface enables emergency egress and alarm monitoring, or it can be used to trigger other auxiliary devices. The fire-alarm disconnect feature is individually selectable for any or all of the 12 outputs. The spade connectors allow you to daisy-chain power to multiple ACMS12 modules, which allows you to distribute the power over more outputs for larger systems.

The PDS16 dual-input power-distribution module is designed to steer the power from two low-voltage AC or DC power sources. The two inputs can be either AC or DC, both DC (12VDC and 24VDC) or both AC (16VAC and 24VAC). That power is distributed over 16 fuse-protected outputs.

As with the ACMS12, the PDS16 spade connectors allow you to daisy-chain multiple PDS16 modules to distribute power over more outputs.

More info:


ASSA ABLOY lists the following components as appropriate for mantrap or interlock applications:

Maglocks: The Securitron M62BD Magnalock is a direct-mounted maglock that has BondSTAT and DPS monitoring. The Alarm Controls 1200LB is a bracket-mounted, single maglock that has an LED status indicator, bond sensor and door status sensor.

Door-position switches: The Alarm Controls CP1-1026 is a DPDT concealed door-position switch. The Securiton DPS-M is an SPST concealed door-position switch. Both are used to monitor the status of a door or to provide an initiate signal.

Electric Strike: The HES 1600CDB-630-DLM has deadbolt and latchbolt monitoring.

Relay Board: The Securitron RB-4-24 is a 24-volt relay board that provides DPDT relays that can be interconnected. This is aimed at interlock installations and where a basic relay board is used to trigger action, shunt alarms or report status from an access control system.

LED Wall Plate: The Alarm Controls RP-09L is a single-gang remote wall plate that has one-half-inch red and green LED status indicators.

Timed Relay: The Securitron TM-9 is a miniature timer that extends momentary switches. It has an adjustable time setting of 2–36 seconds. This is useful for applications that include releasing electric locks and shunting alarm contacts.

Timed Push-Button: The Alarm Controls TS-2-2T single-gang request-to-exit (REX) station, which has a square push-button, provides a convenient way to add authorized access control to a variety of applications. It has illuminated LED and an adjustable timer. The TS-2-2T has two SPDT outputs, one set of momentary and one set of timed contacts. The Securitron EEB2 is a single-gang emergency exit button and has LED status indicators and a fixed 30-second timer. The EEB2 provides additional safety and redundancy as required by code when a motion detector is used as a REX device.

Power Supply: The Securitron AQD2 is a high-efficiency dual-voltage switching power supply. It includes a dedicated battery-charging circuit for the safe charging of optional 12- or 24-volt sealed lead acid batteries. The Securitron AQL4 is an intelligent, multivoltage switching power supply that has optional Netlink monitoring.

More info:,,


Several interlock options are provided by SDC.

UR Series Universal Microprocessor Control Relays are field-programmable multistation access hardware controllers that have six different application modules to allow for  control of multidoor interlocks, mantraps and communicating applications via onboard logic.

UR Series Universal Door Controllers provide a choice of individual dip switch-selectable relay operating modes or system modes for lock control, monitoring, communicating door or lock system logic. Relay output modes can be configured efficiently as a dry contact or a voltage (wet) output. Relays can be configured to work independently or in tandem with an adjacent relay.

You can use the same controller for virtually all multidoor applications. They provide centralized wiring for all locks, access controls, monitoring contacts and peripheral equipment. Onboard logic eliminates the necessity for stand-alone relays. This results in reduced wiring and easy troubleshooting.

Meanwhile, SDC’s CBP Series communicating bathroom control packages are complete kits that include locking devices, a power supply, emergency access push-button switches, a system activation push button switch, status sensors and power-transfer hinges. (The hinges aren’t required for EMLock maglocks.)

More info:

Tim O’Leary is an experienced security consultant and a regular contributor to Locksmith Ledger.

About the Author

Tim O'Leary

Tim O'Leary is a security consultant, trainer and technician who has also been writing articles on all areas of locksmithing & physical security for many years.