The Folly of Maglocks

Maglocks are large electromagnets attached to door frames, paired with metal plates affixed to the doors themselves, to electronically control when doors are locked and unlocked.  They are a common choice for electronically locking doors.  They are also the worst choice.

Most maglocks are well made products that do exactly what they are designed to do.  They solve problems that other locks cannot.  Sometimes they are the only way to electronically secure a door.  So, what is wrong with them?

Most of the problems stem from their nature as an electromagnetic device.  Though all electrified locks depend on electromagnetism, all other types can be classified as electromechanical.  They use electromagnetism (in the form of solenoids) to control the mechanics inside the locks, not to directly hold the doors closed.  Using electromagnetism to directly secure doors leads to a couple of serious problems:

  • Maglocks are always always unlocked when not powered.
  • Maglocks require additional devices to allow exiting.
  • Maglocks require additional devices for emergency entry.

Always unlocked when not powered.  In the security world, the term for this is fail-safe.  Sounds good – your doors should be safe, right?  Well, they should be safe for those inside and secure against those outside.  Choosing a maglock gets it wrong on both counts, because they leave your doors unlocked in an extended power outage (and often during a fire alarm – do you really want someone to be able to unlock your doors by pulling a fire alarm handle?) and. . .

Require additional devices to allow exiting.  Unlike electromechanical locks, maglocks have no inherent mechanical overrides.  To ensure people can safely exit in an emergency, maglock secured doors must (according to fire and building codes, as well as good practice) be equipped with motion sensors and emergency exit buttons, or panic-style push bars, all of which cause the maglock to release.  These add to the expense and complexity of the installation, and often create problems.  We frequently get complaints about this type of motion sensor either allowing anyone to get in by waving something through a gap in the door, or constantly unlocking the door due to people walking past the inside of the door.  This vulnerability is extremely widespread and has been used by penetration testers to get into all sorts of supposedly secure facilities.

Require additional devices for emergency entry.  Unless there is another door nearby that allows access to the same space with a mechanical key, a maglock secured door should be equipped with a keyswitch override on the outside.  In the event of a failure of the access control system, a mechanical key override is necessary to ensure emergency access by firefighters, building engineers, and security guards.  However, having the keyswitch adds another security vulnerability and adds to the installation cost.

So, why use them?  Architects like them because they are sometimes less obtrusive than other lock types.  Especially those of the subset known as shear locks, which are hidden from view when the door is closed, and even more problematic than standard maglocks.  Many people recommend them because they are not familiar with all the other options.  Some installers recommend them because they perceive them as being easier to install than other lock types.  Sometimes the cost is less, but people often forget to factor in the other components that maglocks necessitate.  None of these seem like strong arguments for choosing an inferior way to secure doors.

There are some circumstances where maglocks are the only solution.  A common one is on doors made entirely or almost entirely of glass (commonly referred to as Herculite doors).  I think that limitation, as well as a couple of other vulnerabilities, is a good reason not to use this type of door if security is important.  Most other circumstances that require maglocks are very specialized scenarios, and maglocks may be appropriate if the application is well thought out.

If maglocks are so problematic, what should be used instead?  Check back soon for articles containing the answers.