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Savvy buyers will find bulk buys and other brands online for a little less so as long as they are Lithium and 3000mA or more they should be fine. Don’t use rechargeable AA Lithium batteries – they don’t last and are a pain to change them.

We can’t test battery life, but international reviews suggest up to ten years depending on escape path lighting use and other environmental factors.


The smoke sensor is split-spectrum photoelectric – not ionising. It uses the traditional infrared sensor as well as a new blue LED. This combination, as found in commercial grade detectors, allows it to detect small and large smoke particles

In independent tests, Nest had 100% success rate in detecting both smouldering and flaming fires, and it has a humidity sensor to reduce shower steam false alarms – steam is not smoke!

Nest Protect

In false alarm tests like frying or other flash fires, Nest Protect had an alarm 30% of the time while the other ionisation, photoelectric-ionisation, and photoelectric alarms sounded 48%, 54%, and 55% of the time, respectively.

The Nest benefit is earlier detection of smouldering fires, lower false alarms and a few side benefits.

Side benefits – it is smart too

It has a 10-year lifespan CO (carbon monoxide) detector. CO is known as the silent killer – a deadly by-product of wood or gas burning heaters in enclosed areas.

A microphone automatically tests the alarm once a month – a sound idea. 

A motion detector (120° field of view to 6 metres) can help by illuminating escape paths when you need it. An ambient light detector knows whether its day or night.

The app

The Nest Protect app is available on Android and iOS, and it controls all Nest products.

First, you must create an entirely free Nest Protect account, but you will need a Gmail address.

Why an app? The Nest Protect device works regardless if you use the app or have Internet connectivity. But the app needs Wi-Fi. That allows for room/device naming and interconnectivity with other Nest products like Cams.

Nest Protect

It can tell you things like battery life, alert you to alarms and locations, has a Home or Away Assist (geolocation) and more. I like the email alert feature.

To repeat – you don’t need to use the app to use Nest Protect, but it adds some functionality to a ‘dumb smoke detector’.

Setup is easy

To use the Nest Protect to the app, you need Wi-Fi N 2.4Ghz. Nest Protect uses its own ‘thread’ mesh Wi-Fi between detectors to interconnect, and these have about a 15-metre radius.