Inside the Protect

There’s no ambiguous beeping or mysterious blinking LED on the Protect — the entire product is designed to more clearly communicate what’s actually wrong. When it senses rising levels of smoke, heat, or carbon monoxide, it simply says "heads up," and tell you what’s wrong — Fadell says they picked a neutral phrase to avoid panic if you’re just burning the toast. If there’s something more serious going on, the Protect gets straight to the point and says "emergency" while sounding a horn. Voices include British, Canadian, and US English, as well as Canadian French and US Spanish, and they’re localized: the "heads up" warning is "please be aware" for the British voice, and "attention" in French.

All the voices are female and quite soothing. "Studies have shown that children are less likely to wake up to a horn than the sound of a mother’s voice," says Fadell. Once you locate the problem and decide how severe it is, you can turn off the alarm by simply waving at the Protect, which senses the wave with an ultrasonic motion sensor.

If you have more than one Protect, they’ll all speak and let you know which one has the problem. Smoke in the bedroom? You’ll be told in the living room. The units communicate over Wi-Fi, as well as a secondary low-power RF system in case your network goes down. You can check status and get notifications from the completely rebuilt Nest app for the thermostat and Protect on Android and iOS devices, and in emergencies the app will display a What To Do screen with recommended actions and an emergency phone button. The one thing you can’t do from the app is shut off the alarm; safety regulations require users to do that in person.

"People have this guttural, emotional reaction to the white UFO on the ceiling. They hate it."

The Protect self-tests every 10 minutes and glows green at night to let you know it’s doing fine, and if you walk near one in the dark it’ll light up white to illuminate your path. If you have a Nest thermostat, it’ll use the activity and motion sensors in the Protect to more accurately program when it automatically turns your heat and AC on and off — a boon for people who work at home. And if the Protect senses a carbon monoxide problem, it’ll instruct the thermostat to shut off your furnace.

All of that is great, but I can’t stop asking about the square design, which features a "sunflower" pattern of holes on the front. It doesn’t look like a smoke detector at all — in fact, it looks like nothing so much as a smaller riff on MUJI’s wall-mount CD player. This is the first smoke detector you’ll want to pay attention to.

"People have this guttural, emotional reaction to the white UFO on the ceiling," says Rogers. "They hate it. We wanted something incredibly differentiated."

But the square design wasn’t all about standing out on store shelves. "We will rarely make a decision purely for aesthetics," says Rogers. "We’re not building art, we’re building well-designed products." With the Protect, that meant a sharp focus on one thing. "It’s all about air flow," says Rogers. "Maximum air flow."

Most modern smoke detectors work by shining infrared light through a smoke chamber and measuring the amount of interference in the air. Above a certain level, the alarm goes off. But Nest needed to measure a much wider range to support features like the heads-up warning, and that meant designing a custom smoke chamber and increasing the total air flow.

"It’s not enough to know, hey, there’s smoke in the room, sound the alarm," says Rogers. "We want to know when there’s a little bit of smoke, when something is going on. We designed much more of a dynamic range than any of our competitors ever would." The quest for air flow also means the Protect sits off the wall, with wide vents around the rear edge.

"It’s all about air flow. Maximum air flow."

It’s all very smart, but adding complexity increases the chance of failure — an unacceptable risk for a smoke detector, especially one that promises to be less annoying. So Rogers and his team designed two independent systems for the Protect: a smaller processor to handle the critical safety features, and a larger one to handle communications and intelligence. The two are connected over a serial link, and if the more complicated system goes down, the smaller processor will try to reboot it. If it fails, it’ll sound the alarm.

Perhaps most impressively, the Protect can run all these systems for "multiple years" on six lithium AA batteries. (Nest can’t quote a specific number due to regulatory restrictions; there’s also a hardwired version that uses three AAs for backup.) Nest has always had a formidable advantage when it comes to low-power devices given Fadell and Rogers’ history with the iPod and iPhone, and the Fadell is equally confident about the Protect. "We’re using incredibly low-power processors, the first time they’ve probably ever been used," he says. "We’re in the pico-amps."

There’s some clever power management at work as well: while the wired Protect is in constant contact with the Nest service, the battery-powered Protect only fires up its Wi-Fi radio for about a minute a day to check in with Nest’s servers and upload activity data for the thermostat’s auto-away feature. (The hardwired version is connected all the time.) But if something’s wrong, it kicks into full power and "just starts screaming," says Rogers.

Once the team had its first designs ready, they faced the biggest challenge of all: regulatory approval.