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Comment by ClassyJacket | Hacker News Reader

Any lock that can't be opened from the inside should be illegal as a fire hazard.

I'll amend that to say "can't be opened without the application of unreasonable force". The possibility of a power outage causing the same scenario also worries me.

That's called pushing on the crash bar or twisting the handle/knob so it opens. It's fire code for a reason.

A previous employer's office had electronically locked doors (magnetic, I think?). The studio head said that they were designed to 'fail open' (i.e. unlocked) in the case of a power outage. Then the power went out a couple weeks later, and the doors were locked.

Oops.

Our emergency exits were old-fashioned analog doors and still worked, at least.

Electromagnet locks --- which have an electromagnet in them to keep the door closed and are surprisingly strong for their size --- are truly fail-open since loss of power means loss of force keeping the door locked, but those doors might've also had an additional fail-closed type of electric lock that requires a brief pulse of power to open.

https://en.wikipedia.org/wiki/Electromagnetic_lock

I once worked somewhere with magnetic locks and a decent shove easily opened the door. We did this for smoke breaks as our magstripe cards noted every time we left the control room.

How did you get back in? Sounds like a security hole.

Easy. Just prop it open.

"a decent shove opened the door"

I've installed these doors. It's easy to mess up as the switch to determine the failure mode is part of the equipment. This was an untested install.

How does a mag lock fail closed with no power? Or are you talking about one of those strikes near the latch?

Batteries, I would guess. It's pretty bad if your security system allows entry to people when there is a black out.

Yes, for pretty much any commercial/residential area.

That said, there should be exclusions to such rules for prisons or other areas that are designed to contain people. Some areas need secure doors.

Prisons should have backup power supplies, not electronic locks which fail closed. If there's a fire or flood, better that prisoners are released than trapped in their cells to burn or drown; they were sentenced to imprisonment, not to death.

> Any lock that can't be opened from the inside should be illegal as a fire hazard.

I'm just pointing out the flaw in that statement taken literally.

In theory, in the event of a failure, the guards should still be able to open the cells to release people. I wasn't advocating for fail-impossible-to-open-doors.

Strangely, just two days after I wrote this, my house mate went out and locked me in the house. I had to climb out the window and unlock the door from the outside.

I have a key, but I did not know the one deadlock has a different key for the inside and outside.

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