Smoke alarms play a critical role in keeping your household safe—but like any safety device, they have a limited lifespan. Over time, sensors degrade, batteries weaken, and the risk of failure increases. That’s why it’s important to know how long smoke alarms last, when they need replacing, and what signs to look out for.
In this article, we’ll break down the expected life of different types of alarms, how to check if your alarm is still within its service life, and why timely replacement is essential for protecting your home.
The General Rule: Replace Every 10 Years
Most smoke alarms have a lifespan of 10 years from the date of manufacture. This applies whether the unit is powered by a replaceable battery, a sealed 10-year battery, or is hardwired.
Over time, the internal components of smoke alarms—especially the sensors—can become less responsive. Dust, insects, moisture, and general wear can affect the device’s ability to detect smoke accurately. Even if the alarm still “beeps” when tested, it may not offer reliable protection if it’s past its expiry. If you’d like to test your smoke alarm, read our guide on how to test smoke alarms for proper guidance.
What Affects the Lifespan?
- Environment: Dusty, humid, or insect-prone areas can degrade sensors faster.
- Maintenance: Infrequent testing or cleaning can shorten service life.
- Product Type: Some models have sealed batteries designed to last the full 10 years, while others may require battery replacements during their life.
For the most accurate answer, always refer to the product manual or the label on the back of your alarm.
How to Check Your Alarm’s Expiry Date
Each Cavius alarm includes a date of manufacture and an expiry date—usually printed on the back of the unit. If your alarm is approaching or past the 10-year mark, it’s time to replace it.
Here’s how to check:
- Remove the alarm from its mounting base by twisting counterclockwise.
- Look at the label on the back for a date stamp.
- If the label shows a date more than 10 years ago—or if no date is visible—it’s best to replace the unit immediately.
Tip: If you’re unsure of the age of your alarm, it’s safer to assume it’s due for replacement.
What Happens If You Don’t Replace It?
An outdated smoke alarm may:
- Fail to detect smoke quickly
- Trigger false alarms more frequently
- Stop working altogether
- Lull you into a false sense of security
Relying on an expired alarm puts lives and property at risk. Fires can develop rapidly, and every second counts—so your alarm needs to be fully functional at all times.
Signs It Might Be Time to Replace Your Alarm
Even before the 10-year mark, some signs may indicate your alarm is wearing out:
- Frequent false alarms with no visible cause
- The unit is discoloured, cracked, or damaged
- The test button no longer triggers a full sound
- The alarm chirps even after a new battery is installed
- The LED indicator no longer flashes every 48 seconds (for Cavius models)
If you notice any of these issues, it’s best to replace the unit rather than attempt repairs.
Long-Life Battery vs. Replaceable Battery Alarms
Many modern alarms—like those in the CAVIUS wireless family—feature sealed 10-year smoke alarms, meaning the battery lasts as long as the unit itself. When the battery approaches the end of its life, a short beep every 48 seconds will sound for up to 30 days, giving you time to replace the entire unit.
Traditional alarms with replaceable batteries may still need a new battery each year, but the unit itself still needs replacing after 10 years, regardless of battery status.
If you’re unsure whether your alarm has a replaceable or sealed battery, refer to your product manual or contact the manufacturer for clarification.
How to Replace an Expired Smoke Alarm
Replacing a smoke alarm is straightforward:
- Remove the old alarm from its mounting base
- Purchase a new unit that meets NZ standards (photoelectric smoke alarms are strongly recommended)
- Install the new alarm in the same location, or assess if a better placement is available
- Test the smoke alarm using the test button to confirm it’s working correctly
You can learn more about proper alarm setup in our photoelectric alarm installation guide.
Final Thoughts
So, how long do smoke alarms last? In most cases, no more than 10 years. After that, their reliability diminishes—no matter how well you’ve maintained them. To keep your home and family safe, mark your calendar or set a digital reminder for your alarm’s expiry, and test monthly in the meantime.
If you haven’t checked the age of your smoke alarms recently, now is the time. For more safety tips, visit the Cavius NZ News section or contact us for expert product support.