My Nest smoke alarm was great … right up to the point it went nuts

When smart things go wrong

Hands-on "I thought it was supposed to talk and tell us when the battery was low," my wife said. In retrospect, that was the first sign that all was not well with the Nest Protect smoke and CO detector.

One of the main reasons, in fact probably the reason that the $99 device is on the wall as opposed to one of the many smoke detectors on the market that cost $15-20, is because the device promises to inform you of any problems in a calm and reasonable voice rather than an ear-splitting, piercing scream-beep.

But it was 4:00am, and rather than mention the battery was low, the machine decided to damage our dreams and skulls the traditional way. It woke up the kids, it woke up my wife and led to this bleary-eyed reporter grabbing a stepstool, rotating it off the wall and heading toward the stash of batteries in the cupboard.

Up until this point, the Nest Protect had been great. When you buy smoke and CO detectors, your fervent hope is that you will never hear from them. Nest decided it could do more than that and would make them useful: it has a motion detector that will work with other Nest products and will light up at night if you walk past it. This has been surprisingly useful, removing the need almost every night to turn on a light to highlight the path to the bedroom.

And of course, there was the promise that it wouldn't scream at you if it detected smoke, or chirp at night if its battery was low.

From the Nest website: "No one should be woken up by a low-battery chirp at 2:00am. When you turn off the lights, look for a quick green glow. That's our Nightly Promise. It means all your Nest Protects have tested themselves, the batteries are good, and there won't be any chirps. Sweet dreams."

The Nest Protect takes six AA batteries. Fortunately, due to a battery bulk buy a few weeks earlier, they were ready to hand. The batteries were replaced, the device tested – some more inevitable screaming – and put back on the wall. All was good again.


Except that less than a week later, the Nest informed us – this time with its voice – that the battery was low again. It's a weird thing but when you hear a calm human voice – even one coming out of a plastic box – you tend to want to believe it.

And so, with a skeptical eye, down it came again and six more new batteries were inserted. My wife and I agree on the likely scenario that someone – note the marital diplomacy – had accidentally put some old used batteries in the box with the good ones.

Again, the box goes back to its silent watchdog role.

Until that night, when, on my way to bed and expecting it to turn on and light the way to the bedroom, what should have been a gentle white light turned into an angry red one. And then it started.

"Warning: Smoke detected! Warning: Smoke detected! Alarm will sound in 10 seconds." At the same time, my phone starts buzzing with alerts. Then the piercing scream begins.

This would all be terrifically useful if there was in fact smoke in the house. But there wasn't. Not a whiff. It didn't prevent the house from going into full-on fire mode, however. The wife flies out the bedroom, the kids start yelling, and the Nest Protect sits there in all its red glowing certainty warning us of impending doom.

Fortunately, I remember that if you hit the center button you can mute the alarm – something I immediately do, enabling some measure of sanity to return. And then it is hauled off to a screwdriver for the third time in a week to have its innards pulled out.

Don't panic!

There is a good reason why "shouting fire in a crowded theater" is often held up as an example of the limits on freedom of speech. Even if you do not see a fire, something about being informed there is one causes panic. At the Royal Albert Hall in London, ushers are instructed never to use the term "fire," even if there is one, because of the danger of a rush.

Thanks to the Nest Protect continuing to insist there was smoke pouring out of somewhere – until its power source was yanked out of it – my wife starts checking and double-checking all the rooms. Nothing. Lots of sniffing too. Nothing.

So the box went nuts. And while Nest promises that it will "last up to a decade," it had gone badly wrong in 18 months.

Now, to be fair, this is hardly the first time a smoke detector has malfunctioned. They are mass-produced units and often go wrong, especially over time as dust as other airborne material gets stuck in sensors.

But it's a little different with the Nest Protect. And here's why:

  • It can have an impact far beyond beeping. Nest has a pretty clever system, where the smoke alarm can shut down your house's air circulation (through the Nest thermostat) in order to slow fire spread.
  • It is more expensive. It costs three to four times as much as buying a smoke and carbon monoxide detector. You can't just discard it. And you expect it to last longer and work better.
  • It impacts the app you use for other Nest products. Even though the battery is out of the detector and I even removed it from the Nest app, the home screen – which I also use for my thermostat and security camera – is still flashing red and warning "Smoke!"
  • It raises doubts about whether this smart home tech is such a good idea.

As a general rule, the more complicated devices get, the more often they go wrong. But with smart home technology, the implications are also larger.

If your smart thermostat goes wrong, you could end up roasting or freezing. If your smart lock goes wrong, anyone could enter your home. If your smart lighting goes wrong, you could up in the dark, or with rooms suddenly lighting up. And if your smart smoke detector goes wrong, you could end up in a panic in the early hours of the morning.

All the additional benefits that smart-home tech brings can very quickly turn into extra problems if they go wrong. The Nest Protect comes with a two-year warranty. Our house is still undecided about whether to ask for a replacement or go with the dumb detectors that do less, but with less fuss. ®

Updated to add

A Nest spokesperson has been in touch to say...

We were sorry to hear about Kieren’s experience, as we want everyone to enjoy their Nest products. Here’s some guidance on how to mitigate the issues that Kieren reported in his story.

Kieren experienced the false alarm issue with a first-generation Nest Protect, which has been off the market since last year, when we replaced it with the second-generation Nest Protect. The new model has been completely redesigned and addresses this issue. In fact, it is our highest rated product with a 4.6 star rating on If customers are having a false alarm problem with a first-generation model, they can reach out to Nest Support 24/7 for a replacement with the latest version.

It’s also important to use the right batteries in Nest Protect. Nest Protect is designed for Energizer L91 lithium batteries, which provide far more power than the conventional AA batteries, and are designed for multiple years of operation. We highly recommend customers use these batteries since Alkaline batteries will not last as long.

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