How to Replace the Batteries in Your Smoke Alarms

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An easy guide to wired and non-wired smoke detectors
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Smoke detectors are an essential piece of safety equipment for any home. Properly maintaining your smoke detector—including changing the batteries twice a year—can help protect your family in the event of a fire. We talked to firefighting expert David Decker and licensed electrician Marvin Woo to learn everything you need to know about changing the batteries in non-wired and wired smoke alarms, plus tips on properly testing and maintaining your alarm .

How do you change the batteries on a smoke detector?

Firefighting expert David Decker recommends changing the batteries in your smoke alarm twice a year. To do that, remove the cover, then unplug the wiring harness if you have a hardwired detector. Remove the battery cover and the old batteries, install the new batteries, and reassemble the alarm.

Section 1 of 5:

Replacing the Battery in Non-Wired Detectors

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  1. The exact way to remove the smoke detector cover will depend on the device you have. On most smoke detectors, remove the cover by rotating the cover counter-clockwise about a quarter of a turn. Then, pull straight down to remove it.
    • If your smoke detector has a battery compartment on the front of the cover , you do not need to remove the cover to change the battery.
    • If your smoke detector has a tamper-resist feature , you may need to disengage it by pressing a tab with your fingers or a screwdriver. [1]
    • If the cover is connected to the base by wires , skip to our section on wired smoke detectors .

    Meet the wikiHow Experts

    David Decker is a former firefighter and assistant fire chief, with over 32 years of experience. He now owns Command Vision, a fire training company.

    Marvin Woo is a licensed electrician and the owner of Woo’s Electrical and Appliance. He has over 2 decades of experience.

  2. The battery compartment can be located on the front, side, or back of the cover, and the exact way you open it will vary depending on the model. If you’re not sure, check your smoke detector owner’s manual (or look up the manual online). Options for opening a battery compartment include:
    • Sliding or prying off the cover with your fingers
    • Pressing in on a tamper-proof tab with your fingers or a screwdriver [2]
    • Removing a screw, then sliding off the cover
    • Pushing in on the compartment so the door swings open
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  3. If your smoke detector has a 9V battery, pull it straight out to remove it. If it has AA batteries, gently pry them out, starting with the negative end. Then, install the new batteries, double-checking to be sure the positive and negative terminals match the ones in the compartment. [3]
    • Woo says, “Battery trays are always stamped or labeled with a + and - sign that shows which way to insert the batteries.” [4]
    • If the battery compartment doesn’t close properly, double-check the alignment of the batteries. Some smoke detectors have a feature that prevents the door from closing if the batteries are in improperly.
  4. This should be the opposite process you used to remove the cover and battery compartment. For instance, you might slide or snap the battery cover back into place. [5]
    • To replace the cover, you’ll typically need to place it back on the base, then give it a quarter-turn clockwise.
  5. Before you reinstall the smoke detector, make sure that the batteries are working properly. To do that, press the test/silence button on your detector until the alarm sounds. This button is usually on the front of the detector. [6]
    • Most test buttons require you to press the button for a few seconds to engage the test.
    • If the alarm doesn’t sound when you’re testing the batteries, check that they’re lined up properly. If they’re in correctly but the detector still doesn’t work, try again with new batteries.
    • If the smoke detector still doesn’t work even with new batteries, replace the entire alarm with a new one—it may be defective or expired. [7]
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Section 2 of 5:

Changing the Battery in Hardwired Smoke Alarms

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  1. Hardwired smoke detectors are connected directly to your home’s power supply. The battery in these detectors is intended to power the alarm in the event of a power outage. To prevent electrical shock, turn off the appropriate circuit before you attempt to change the battery. [8]
    • Many homes with hardwired circuit breakers will have a breaker specifically labeled for smoke alarms. But if your breakers aren’t labeled, press the main breaker to cut all power to your house, including the smoke alarm.
    • Most hardwired smoke detectors have a small green light that’s on when it has power—double-check that this light has turned off after you switch off the circuit.
  2. The way you do this will depend on the kind of smoke detector you have in your home. If you’re not sure how yours works, check the user manual (or search online for the manual if you don’t have yours anymore). Some common covers include: [9]
    • Push-lock covers: Look for an arrow indicating the point you need to push, then use a thin screwdriver or pen to release the push-lock.
    • Twist-lock covers: Twist the cover (usually counterclockwise). In some cases, you may need to push upwards and twist. Hold the alarm as you remove this kind of cover—once the lock is undone, the cover will fall downwards.
    • Friction-lock covers: These covers are held in place by a plastic locking mechanism on the inside of your detector. Pry the cover free with your fingers using firm, moderate-light pressure.
  3. Look for a clip at the point where the wires meet the detector cover. Typically, to remove the wiring harness, squeeze the prongs on the sides or the front and back of the clip. After you release the clip, tug on the harness with gentle but firm pressure to pull it free.
    • Don’t yank on the wires, or you could damage them.
  4. Pull out the old battery—usually either AAs or a 9-volt. Replace them with new, high-quality batteries. Double-check to be sure that the + and - terminals are lined up correctly based on the markings inside the battery cover. [10]
  5. Use the opposite procedure you used to remove your smoke detector cover to fit it back into place. Replace the battery cover, then snap the wiring harness back into place and seat the cover back in the base. Once the cover is on, press the button on the front of your smoke detector to test the battery. [11]
    • Most smoke detectors have a button on the center of the cover. In many cases, to test your smoke detector, all you need to do is press this button for five seconds. You should hear a chirping noise if your battery is good and properly installed.
    • If you find that, no matter how you fit your battery into place inside your smoke detector, the detector still will not give a test-chirp, try another battery. If this battery does not work, you may need to install a new smoke detector.
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Section 3 of 5:

What if I can’t remove the battery on my smoke detector?

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  1. Sealed smoke alarms contain a lithium battery that’s designed to last for 10 years. After the 10 years are up, you replace the whole smoke detector .
    • Be sure to test your smoke detector regularly, even though you don’t need to replace the battery.
Section 4 of 5:

Testing and Maintenance Schedule

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  1. Decker says, “All smoke detectors should be tested once a month, and we recommend changing the battery twice a year. Try changing your battery every time you change your clocks for daylight savings time to ensure your smoke detector is working correctly.” [12]
    • If your smoke alarm is chirping, replace the batteries even if it’s been less than 6 months since the last time you did it.
    • Replace your entire smoke alarm every 10 years. Check the back of the smoke detector for the date it was manufactured. Replace it with a new unit after 10 years or if it stops working properly. [13]
    • Regularly dust or vacuum your smoke detector. Dust or grease buildup can block the sensor and prevent it from working properly. [14]
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Section 5 of 5:

Where to Place Smoke Detectors

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  1. Decker says, “We recommend having a smoke detector in each bedroom and in the hallways. You should also have one on each floor. That way, you have an early notification if there’s a fire in your home, and it gives you plenty of time to get out.” [15]
    • “Don’t put smoke detectors by doors, windows, or air ducts,” adds Decker. “Fresh air can prevent smoke from getting to the smoke detector, which can cause it to trip.” [16]
    • Place smoke detectors on or near the ceiling because smoke rises. [17]
    • To prevent unnecessary alarms, avoid placing smoke detectors in humid areas or within 10 ft (3.0 m) of where you cook.
    • Have a professional electrician install hardwired smoke detectors. [18]
    • If your existing smoke detectors don’t fit these guidelines, either relocate them or add more.

Community Q&A

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  • Question
    What do I do if the smoke detector still chirps with a new battery?
    Community Answer
    Check to see if it was activated by mistake first. You may have to get a new smoke detector.
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  • Question
    How do I stop my smoke alarm from beeping every two minutes for no reason?
    Community Answer
    Most probably the alarm is "chirping" because the battery is flat and needs replacing. Put in a new battery and that should resolve it. Otherwise, read the instructions printed into or on the alarm or that accompanied the alarm.
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    Not Helpful 18 Helpful 19
  • Question
    I've replaced the battery in a wired smoke detector, but it keeps chirping. What should I do now?
    Community Answer
    Try to vacuum out any dust caught in the sensor. If that doesn't work, my manual says to replace it with a new one. Better to be safe than sorry.
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    Thank you for your feedback.
    If wikiHow has helped you, please consider a small contribution to support us in helping more readers like you. We’re committed to providing the world with free how-to resources, and even $1 helps us in our mission. Support wikiHow
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      Tips

      • Even if your smoke detector is directly wired into a power source, it likely has a backup battery that needs to be replaced yearly.
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      • Some smoke detectors will alert you that the batteries need to be changed by sounding the alarm. If your smoke detector is sounding in the absence of smoke, it may need a battery replacement.
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      • Don't remove the battery or disable your smoke alarm.
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      References

      1. ↑ https://www.electricbargainstores.com/v/vspfiles/PDF_spec/Firex/firex-4618-manual-english.pdf
      2. ↑ https://www.tycosafetyproducts-anz.com/public/Datasheet/15204_B1_OSID_Product_Guide_A4_IE_lores.pdf
      3. ↑ https://www.dover.gov.uk/Housing/Housing-for-Tenants/Resident-Information/Fire-Safety/Test-Your-Smoke-Alarm.aspx
      4. ↑ Marvin Woo. Licensed Electrician. Expert Interview
      5. ↑ https://www.dover.gov.uk/Housing/Housing-for-Tenants/Resident-Information/Fire-Safety/Test-Your-Smoke-Alarm.aspx
      6. ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/06/what-kind-of-smoke-alarm-smoke-detector-should-i-buy
      7. ↑ https://www.dover.gov.uk/Housing/Housing-for-Tenants/Resident-Information/Fire-Safety/Test-Your-Smoke-Alarm.aspx
      8. ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/06/what-kind-of-smoke-alarm-smoke-detector-should-i-buy
      9. ↑ https://www.nfpa.org/news-blogs-and-articles/blogs/2023/03/06/what-kind-of-smoke-alarm-smoke-detector-should-i-buy
      1. ↑ https://www.dover.gov.uk/Housing/Housing-for-Tenants/Resident-Information/Fire-Safety/Test-Your-Smoke-Alarm.aspx
      2. ↑ https://www.dover.gov.uk/Housing/Housing-for-Tenants/Resident-Information/Fire-Safety/Test-Your-Smoke-Alarm.aspx
      3. ↑ David Decker. Firefighting Expert. Expert Interview
      4. ↑ https://www.usfa.fema.gov/prevention/home-fires/prepare-for-fire/smoke-alarms/#care
      5. ↑ https://www.security.org/home-security-systems/smoke-alarm-chirping/
      6. ↑ David Decker. Firefighting Expert. Expert Interview
      7. ↑ David Decker. Firefighting Expert. Expert Interview
      8. ↑ https://www.dla.mil/About-DLA/News/News-Article-View/Article/2393714/fall-back-change-your-clocks-batteries-during-daylight-saving-time/
      9. ↑ https://www.usfa.fema.gov/prevention/home-fires/prepare-for-fire/smoke-alarms/#placement

      About This Article

      Article Summary X

      To change the batteries in your non-wired smoke detector, start by removing the detector from its mounting on the ceiling either by twisting or sliding it out. Then, open the covering to access the battery inside. Make sure you check to see which type of battery your detector needs, since it will fail if you replace the existing battery with the wrong kind. When you install the new battery, make sure the negative and positive terminals match up with the markings on the detector before closing the cover. Before you return your smoke detector to its mounting, press the button on the detector to test the battery and make sure you’ve installed it correctly. For tips on how to change a battery in a wire smoke detector, keep reading!

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        Mar 20, 2016

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