Nest Protect Review – 2nd Gen Smart Smoke Plus Carbon Monoxide Detector

We gave the Second Generation Nest Protect Connected Smart Detector our top pick for best device in our recent review of Best Smoke and Carbon Monoxide Detectors (the list included First Alert, Ecobee, Birdi, Halo smart labs, Roost, Netatmo and others). Here we continue with a full review of all the features for the wired and battery-operated Nest Protect Alarms.

The Nest Protect is  available in both battery powered, and direct wired (with a battery back-up) to your house electrical. You also have a choice of colors: White or Black. Here are the links and spot prices on Amazon:
Nest Protect Smoke Plus Carbon Monoxide Alarm, Battery Powered (Second Generation) ($119.00)
Nest Protect Smoke Plus Carbon Monoxide Alarm, Wired 120V S2001LW ($160.00)

With the Battery Powered device, Nest includes the required six (6) lithium AA batteries, which are designed to last five years. These are replaceable, and you should always use lithium batteries in the Nest.

In addition to detecting smoke, heat and carbon monoxide, the Nest Protect’s sensors can detect humidity, motion / room occupancy, and ambient light.

Smoke detection is accomplished through their “Split-Spectrum Sensor” technology. The Split-Spectrum Sensor enhances a traditional infrared photoelectric sensor with a second, blue LED, to detect a wider range of particle sizes in the air. While this technology has been used in commercial grade alarms, it wasn’t until now used in residential alarms. Tests at Nest labs suggest these sensors are supposedly better at detecting smoldering fires, which are the leading causes of at home incidents.

Regardless of whether you get a smart detector or a standard one, they all rely on two basic types of sensors to detect a “smoke event”: ionized and photoelectric. Ionized detectors are cheaper but more prone to false alarms than their photoelectric counterparts. Ionization sensors respond slightly quicker to fast-burning fires, while photoelectric sensors are faster at detecting smoldering fires (the more common type in homes). Ionization sensors are more prone to nuisance / false alarms, making them more likely to be disabled by the home’s residents and leaving that house at greater risk. Ionization alarms are not recommended for use in kitchens or near bathrooms due to a higher likelihood of false alarms in these areas. Conversely, photoelectric sensors help reduce false alarms such as from cooking or shower steam.

Here is a run-down of all the Nest Protect sensors and basic features:

Carbon monoxide sensor: detects carbon monoxide (CO), an odorless, colorless and potentially deadly gas. The CO electrochemical carbon monoxide sensor lasts up to 10 years. You’ll get a fast chirp signal, as well as an alert to your smart device when the sensor at its end (at which time you’ll need to replace the Nest, since you can’t just replace the CO sensor).

Heat sensor: enables Nest Protect to detect sudden rises in temperature. This sensor has a ± 1.8ºF (± 1ºC) resolution, which is more than sufficient to alert you to a drastic temperature flare up as would happen in a fire.

Humidity sensor: enables Steam Check. This Nest Protect exclusive feature uses an advanced software algorithm to reduce nuisance alarms caused by things like steam from your shower. The Steam Check can also be disabled / enabled through the Nest app. Resolution is ± 3%RH (relative humidity).

Occupancy sensor: detects when you are walking under Nest Protect to turn on Pathlight and light your way in the dark.  The sensor has a 120º field of view to 20 feet, giving you a wide coverage area. It briefly turns on when you walk by your Nest Protect, then turns off again after you’ve passed. Pathlight uses high efficiency LEDs  to help conserve battery life in non-hardwired units. You can also change Pathlight’s settings with the Nest app, to control how long it stays on, as well as completely disabling the feature (useful for battery operated devices in high traffic areas). And if you have a Nest Learning Thermostat, the occupancy sensor also helps with Home/Away Assist, so you can save energy while you’re gone.

Ambient light sensor: tells Nest Protect when you’ve shut off the lights for the night so it can automatically turn on Pathlight and Nightly Promise: Each night when you turn out the lights you’ll get a quick green glow which means the batteries and sensors of Nest Protect are working. This means no dreaded chirps at 3 AM, so you can sleep safe and sound. Nest Protect constantly monitors its internal sensors, batteries and Wi-Fi connection. And if you have more than one Nest Protects in your home, and have them connected (which you should!), Nightly Promise doesn’t just let you know if the alarm nearest you is working. It shows you the status of every Nest Protect in the house.

Microphone: enables Nest Protects to test their speaker and horn automatically each month, or any time you want to run a test. The omnidirectional microphone is rated at 70 dBA SNR (signal to noise ration). This test feature is called Sound Check. During Sound Check, Nest Protect makes a short sound and listens with its microphone to confirm that its speaker and horn are working. The whole test is over in less than 5 seconds. Note, in the Nest app, you can schedule the automated monthly test to run when you’re likely to be away from home and so it won’t disturb you. If you have more than one Nest Protect, they’ll all run a Sound Check at the same time. Think about your current detectors, and when was the last time, if ever, that you tested them? If you are like me, it’s only when the low battery chip started (and why is that always in the middle of the night?) that you gave your detectors any attention.

Speaker: A single 2 Watt speaker provides voice prompts to indicate which device has triggered an alert, and what type of alert (e.g., fire, CO, etc.). You can set a custom name for each room / location, so that when the detector talks, you’ll know exactly where the issue is and can take appropriate action.

Horn: 85dB SPL (sound pressure level) at 10 feet (3 m); Yes, this is plenty loud.

If something does trigger the device, you’ll get a standard high-volume alarm and you’ll also get a talking voice to tell you which room is being affected. The Nest will also tell you what type of alert it is. And, the 6 LED RGB light ring will change color on the Nest so you get a visual identification of the alert type, and which unit is affected.

All this by itself is pretty amazing, but only a bit more than you might get on a high-end standard detector. Add in the “smart” part, and that is where the real value of the Nest Protect comes in. The Nest works with Amazon Alexa, Google Home, Philips Hue, Lutron, Win and “IFTTT”. And, as you would expect, it works with all other Nest products (see our article on the current list of What Works With Nest).

There are two levels to the Nest connectivity. The first is through it’s own network to allow all of the Nest devices in your home to talk with one another. So if one device is set off, it will spread the message to all the other connected devices, setting them off as well. This internal network use a proprietary protocol (“Weave“) over a 250 kbit/s IEEE 802.15.4 low-rate wireless personal area network (LR-WPANs) standard. So even if you’re power goes out, or your WiFi network stops working, the Nest devices are still communicating with each other. All your Nest Protects can communicate if they’re within about 50 feet (15m) of each other inside your home. If range is an issue, you’ll need to add more Nest Protects to establish a network.

One thing to keep in mind, the Nest wireless Interconnect will not work with other brands of alarms. This is generally true for all brands of smart alarms – they only work within their family of devices. For your safety and best protection, use the same brand of smoke / carbon monoxide alarm throughout your home.

The second level is connecting your house to all your smart devices, computers, monitoring services and the rest of the outside world. Nest works with your standard home WiFi network using the familiar 2.4 GHz / 5.0 GHz IEEE 802.11 b/g/n. With an app on your iPhone / iPad / Android device you can set up how alerts are sent, who gets an alert, and the ability to monitor your home in real time.

With the app, your can also test your Nest devices as well as silence a device for a false alarm.

If you have other Nest products, or compatible devices, you can do even more. For example, coupled with a Nest Thermostat ($235 on Amazon), you can set up the Nest Protect to instruct the Nest Thermostat to shut down your HVAC / ventilation system if smoke or fire is detected. If you have a Nest Security Camera ($185 on Amazon), you can have one, any or all of the cameras start recording when an incident occurs. And have your monitoring service notified.

Other noteworthy benefits:

  • Push alerts to phones, and silencing an alarm from a phone can be done in under 30 seconds. Other smart devices can take up to 2 minutes, a long time when your house is screeching at you from all devices.
  • Customization of each device to have it’s own room / location name. Most other devices only let you choose from a selection menu of about a dozen options.

Issues with Nest Protect:

  • One of the most expensive devices.
  • Only has 2-year limited warranty, compared with 5- and 10-years of other smart alarms.

Final thoughts on Nest Protect – this is the top of the line for smoke, fire and CO monitoring, and worth the cost if you have the budget to outfit your home with these devices. The features and benefits merit the price, and the availability of other devices in the Nest product family to inter-operate with is the largest available from any brand.

Here’s a short (90 second) promo video for the highlights of the Nest Protect:

Buy the Nest now through Amazon, in either the house-powered or battery-powered, in Black or White:

Nest Protect Smoke Plus Carbon Monoxide Alarm, Battery Powered (Second Generation) ($119.00)
Nest Protect Smoke Plus Carbon Monoxide Alarm, Wired 120V S2001LW ($160.00)

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