# How strong are those magnetic door locks? **URL:** \ **Category:** Factual Questions\ **Created:** [December 20, 2007, 11:33pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767 "2007-12-20T23:33:47Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [December 21, 2007, 7:11pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767/21 "2007-12-21T19:11:48Z")
They are engineered to accept a fair degree of misalignment, as door hardware endures wear, abuse, and such. The tests which these products must endure to achieve a UL listing are quite exhaustive. ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [December 21, 2007, 7:29pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767/22 "2007-12-21T19:29:07Z")
[QUOTE=danceswithcats] That depends. First, is the system designed to fail ‘safe’ or fail ‘secure’? If safe, then the locks would allow egress. If secure, then they must have a backup power source, either for the security system, or for the facility. [/QUOTE] In a fail secure system, is the door held shut by the magnets, or held open? ---
**Author:** ![minor7flat5](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/minor7flat5/32/258_2.png) [@minor7flat5](https://boards.straightdope.com/u/minor7flat5)\ **Post date:** [December 21, 2007, 7:41pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767/23 "2007-12-21T19:41:03Z")
[QUOTE=Raguleader] So the doors slam in sequence? That’s cool. It’d be cooler if they slid down from the ceiling, like in Star Trek II and VI. 🆒 [/QUOTE] We have a research library at work (one of Jersey’s “Big Pharma” companies) and they designed the library with a specific fire rating. In order to keep this rating, right in front of the glass doors going in to the library there is a wide slot in the ceiling where there is a guillotine-style steel door that will come down in case of fire. Just like in the movies. I have never seen it tested, but it would be totally cool to watch that door come slamming down. Of course, nothing can beat those three-foot-thick fire doors that separate the hanger bays in a modern aircraft carrier. There’s bright striping on the floor showing the danger zone where you don’t want to be if they hit the button and the doors begin to slam shut. I did watch them testing those doors and they move pretty quick. > [@danceswithcats](#): > > They are engineered to accept a fair degree of misalignment, as door hardware endures wear, abuse, and such. The tests which these products must endure to achieve a UL listing are quite exhaustive. That’s a fairly generic statement that can be said about almost any product. Specific to these door locks, what kind of testing do they do? Is it done to failure? (I’m not trying to be a pain. I imagine you _do_ have more detail and am interested in hearing about it.) ---
**Author:** ![Merijeek](https://avatars.discourse-cdn.com/v4/letter/m/f05b48/32.png) [@Merijeek](https://boards.straightdope.com/u/Merijeek)\ **Post date:** [December 21, 2007, 8:07pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767/24 "2007-12-21T20:07:58Z")
[QUOTE=SmackFu] In a fail secure system, is the door held shut by the magnets, or held open? [/QUOTE] When the system **fails** , the system is **secure**. Which means you’re gonna die in the fire. In a fail safe system, if the system **fails** it defaults to **safe** so the killers can come in and get you. Wait, no, that’s not it. -Joe ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [December 21, 2007, 8:54pm UTC](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767/25 "2007-12-21T20:54:31Z")
[QUOTE=SmackFu] In a fail secure system, is the door held shut by the magnets, or held open? [/QUOTE] The maglock devices themselves will \*\*fail safe - they immediately unlock \*\* if there’s a power failure or their wiring is cut or damaged. If the overall system they’re part of has power backup, then they should stay locked during a power failure until the battery runs down. Some localities require an exit door with a conventional crash bar as an emergency backup in case the maglock control system does not release or fail. The technology is relatively new, and as such, not completely trusted by some jurisdictions. Compare this to something like a solenoid-operated lock, such as the “buzz you in” kind used on seemingly every apartment building’s front door. That will **fail secure - it stays locked** if the power goes out or the wiring is damaged, but you can still use your key from the outside to open the door, or use the crashbar / knob from the inside to open the door, so a failure of the device isn’t likely to lead to loss of life. You need to look at what’s being secured, who’s being kept in or kept out, and what backup or compensating controls (eg: crash bars, armed security guards, other conventionally locked doors, etc.) are available. [Previous page](https://boards.straightdope.com/t/how-strong-are-those-magnetic-door-locks/430767.md?page=1)