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If you’re a homeowner, it’s important to know when your smoke detectors expire. If they’ve already passed the expiration date, don’t worry! You can simply purchase you new devices online and have them installed in your home by the end of the week.

Quick Tip:

The date on the back of your smoke detector is probably not the expiration date. That is usually the manufacturing date.

Why do Smoke Detectors Expire in the First Place

Smoke sensors within the device can become less responsive to smoke particles after about ten years. This is the reason that even if your alarm is functioning when you test it, all manufacturers recommend changing the device,

Since we wouldn’t want a dull smoke detector to alert us of a fire later than it should have, we take this recommendation very seriously. In addition, if a home owner does not change smoke detectors according to the expiration date they might be liable for damages in cases of fires.

Each manufacturer has placed the label in a slightly different place. To facilitate the process of finding this information we’ve compiled all the information your need for each of the main smoke detector manufacturers.

How to Find Expiration Date on First Alert Smoke Detectors

First of all, as mentioned earlier many people will get confused with the date on the back of their smoke detector thinking that this is the expiration date. This is in fact usually not the case.

See the below image of the First Alert device. The date with the red rectangle is the manufacturing date.

So how do you know if your First Alert smoke detector is expired?

First Alert specifies on their website that their smoke detectors last anywhere between 7 and 10 years. So at about the 7 year mark the device’s ability to detect smoke will start getting worst.

  • If your smoke detector is less than 7 years old: Test the alarm button. If all functions well there is no need to change the device
  • If your smoke detector is between 7 and 10 years old: Test the alarm button. If all functions well, it is up to you whether you want to change your device now or in a few years.
  • If your smoke detector is more than 10 years old: You have to replace the device despite it functioning properly according to the tests.

So if the date on the back of the device is over 10 years ago, your smoke detector is too old and needs to be replaced.

If you are reading this page because the alarm does not seem to be functioning properly, check your warrantee. Smoke detectors usually come with very long warrantees. You might be eligible to get a free new device.

How to Find Expiration Date on Kidde Smoke Detectors

It’s much easier to figure out if a Kidde detectors is expired. The expiration date is written directly on the back of the unit in black ink. The code is next to “Exp,” and represents the month and year that it expires.

Similarly to our instructions for the Kidde devices, if your smoke detector works properly when pressing on the test alarm button, you don’t need to switch the device.

If your device is expired, you absolutely need to purchase a new device.

How to Find Expiration Date on Nest Smoke Detectors (from app and device)

Unlike the two previous smoke detectors the Nest Protect has a cool app, which can also give you the expiry information you need.

Finding the expiration from the app:

  1. Open the app and go to it’s home screen
  2. Tap on the Protect button
  3. Tap on the Settings (which has the wheel symbol)
  4. Finally, tap on Technical info

On this page you’ll find the expiration date next to “Replace By”

If you find the app option too complicated, the Nest also allows you to find the expiration date on the back of the device itself. This however will require you to take the device off the ceiling.

  1. First step, twist the device counter clockwise to disconnect it from its back plate
  2. Next, look for the words “Replace by” on the sticker.
Replace by date


Smoke detectors are an important safety device in any home, but most people unfortunately don’t make sure that their devices function properly.

If you’ve determined that you need to switch your smoke detector please our other articles on the best smoke detectors of 2021. For instance, here is our article on the best smart smoke detectors of 2021.

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