If the device detects a sufficiently-high level of smoke, the button is ignored.

Yes, this is infuriating. It happens on my networked system of smoke alarms. It ignores the hush for nearly a minute while the smoke clears out. Ridiculous. Makes me want to just disconnect all of them.

Again with this statement, accompanied by absolutely no citation.

I recently purchased a non-Nest smoke alarm. The documentation explained that if there was an alarm, the hush button would silence it temporarily, but if there was a high level of smoke, the hush button would not work and the alarm would not be able to be silenced.

Since both Nest and other smoke alarm companies say this, I conclude there is some regulation to this effect.

The Nest device in the video did not appear to be experiencing high levels of smoke.

Found a citation: https://news.ycombinator.com/item?id=9064731

I posted a link to the citation in the root comment of this thread.

Since I can't actually see the document, does it say that the fire alarm can't be muted even in heavy smoke? Or are you just guessing that it might? I would find that surprising.

I found the relevant citation: https://news.ycombinator.com/item?id=9064731

I don't know. UL doesn't make their rules openly-available. You have to pay them to read them.

But Nest's website says UL's rules forbid the silencing, and I see no reason to think Nest would lie about it.

Sorry; I meant a citation to the actual law people are referring to, the one that says smoke detectors shall not be capable of being manually silenced in the presence of smoke.

Smoke detector user manuals might vaguely allude to such a law to justify crappy engineering, but that's not the same as a citation to specific Federal, state, or municipal codes, or even an insurance underwriting code.

The actual law is "Do what UL says". Or, to use a direct quote:

"The U.S. model codes and installation standards require smoke alarms and smoke detectors to be listed in accordance with the Standard for Single- and Multiple-Station Smoke Alarms, UL 217, and the Standard for Smoke Detectors for Fire Alarm Signaling Systems, UL 268."

http://osfm.fire.ca.gov/firelifesafety/pdf/Smoke%20Alarm%20T...

I'm missing the part that justifies what we see in that video. He's unable to mute the detectors, but there seems to be a distinct lack of smoke.

Why are people carrying water for this idiocy? Nothing in the document you linked has anything to do with the subject at hand. Fine, whatever, you're not supposed to be able to mute the detector in the presence of heavy smoke. But there is absolutely no prohibition against a mute feature in general.

I found a citation that I think even you will accept:

https://community.nest.com/message/36003

True, and the 4% business was also mentioned in the summary document earlier. That doesn't change my two underlying points: (1) it's an incredibly stupid regulation that seems to have been designed to cause people to remove the battery or otherwise disable their smoke detectors permanently to avoid nuisance alarms; and (2) there was no smoke at any level in this scenario.

Poor engineering on Nest's part led to a situation where a poorly-thought-out regulation came into play. Neither condition is defensible... yet look at all of the people in this thread trying to defend one or both.

(Yes, I'm moving the goalposts to a certain extent, as I was mistaken about there being no law against silencing a smoke detector in the general case.)

Worse, municipalities are starting to pass stricter code, requiring the battery to be unremovable:

http://rules.cityofnewyork.us/tags/smoke-alarm