Replace the battery by opening the alarm cover, removing the old battery, and inserting a new one of the same type

Most First Alert smoke alarms use a 9-volt battery that slides or clicks into a holder inside the unit. The whole job takes about two minutes. Open the alarm cover by twisting it counterclockwise or pressing the release tab on the side—the manual that came with your alarm will show which. Remove the old battery by gently pulling it straight out of the connector, then insert the new 9-volt battery with the terminals facing the same direction the old one was facing. Close the cover by twisting clockwise or pressing until it clicks.

After you install the new battery, the alarm should chirp once to confirm power. If it does not chirp, the battery may be inserted backward or the connector may be loose. Remove the battery, wait five seconds, and reinsert it firmly until you hear the click or feel it seat.

Key Takeaways

  • First Alert alarms typically use a 9-volt battery, though some models use AA or AAA batteries—check your manual or the battery compartment label to be sure.
  • The cover twists counterclockwise on most models, but some have a release tab on the side that you press instead.
  • A single chirp after battery installation means the alarm has power; silence or a chirping pattern means the battery is not seated correctly.
  • Replace the battery once a year, or whenever the alarm chirps every 30 to 60 seconds to signal low battery.

Locate the battery compartment on your alarm

The battery compartment is usually on the back or bottom of the alarm unit. If your alarm is mounted on the ceiling, you may need a step stool or ladder to reach it safely. Look for a circular cover with a small arrow or the word "open" printed on it. Some First Alert models have the compartment on the side instead of the back.

If you cannot find the compartment, check the manual that came with the alarm. You can also search the First Alert website by your model number—the number is printed on a label on the back of the unit. The manual will show you exactly where the battery goes and what type your model uses.

Open the alarm cover without forcing it

Most First Alert covers twist counterclockwise. Place your thumb and fingers on opposite sides of the cover and turn gently. Do not force it—if it does not turn easily, you may be turning the wrong direction. Try twisting clockwise instead, or look for a small tab or button on the edge of the cover that you press to release it.

Some newer models have a push-to-release tab on the side of the cover. Press this tab while gently pulling the cover away from the unit. Once the cover is open, you will see the battery holder inside, usually a plastic clip or socket with two metal terminals.

Remove the old battery and note its orientation

Grasp the old battery by its sides and pull it straight out of the holder. Do not touch the metal terminals on the battery or the connector inside the alarm. Note which direction the terminals were facing—the positive terminal (marked with a plus sign) should face the same way when you insert the new battery.

If the battery is stuck, do not pry it with a metal tool. Instead, gently wiggle it side to side while pulling. If it still will not budge, stop and consult the manual—you may have the wrong compartment open.

Insert the new 9-volt battery correctly

Hold the new 9-volt battery so the terminals face the same direction as the old one did. Slide the battery into the holder until you hear a click or feel it seat firmly. The connector should grip the battery terminals snugly. Do not force the battery in—if it does not slide smoothly, remove it and check that the terminals are aligned with the connector.

Once the battery is seated, the alarm should emit a single chirp or beep. This chirp confirms that power is flowing to the unit. If you hear nothing, remove the battery, wait five seconds, and reinsert it. A continuous chirping sound (every 30 to 60 seconds) means the battery is low and needs replacement even though it is new—this can happen if the battery itself is defective.

Close the cover and test the alarm

Twist the cover clockwise until it stops, or press the release tab until it clicks into place. The cover should sit flush against the alarm body with no gaps. Do not overtighten—turn only until you feel resistance.

Press the test button on the front of the alarm to confirm it is working. You should hear a loud alarm sound for a few seconds. If the alarm does not sound, the battery may not be making good contact with the terminals. Open the cover again, remove the battery, and reinsert it firmly. Test again after reinserting.

Know when to replace the battery again

First Alert recommends replacing the battery once per year, even if the alarm has not chirped. Mark your calendar or set a phone reminder for the same date each year—many people choose their birthday or the day they change their clocks for daylight saving time.

If the alarm chirps every 30 to 60 seconds, the battery is low and needs replacement right away. This chirp is a signal that power is running out, not a sign of a fire. Some First Alert models also have a red LED light that blinks when the battery is low. Replace the battery as soon as you hear the chirp or see the light, because the alarm will not detect smoke if the battery dies.

Frequently Asked Questions

What type of battery does my First Alert alarm use?

Most First Alert smoke alarms use a 9-volt battery, but some models use AA or AAA batteries instead. Check the label inside the battery compartment or on the back of the unit. If you cannot find the label, look up your model number on the First Alert website or in the manual.

Why does my alarm keep chirping even after I put in a new battery?

The battery may not be seated firmly in the connector. Remove it, wait five seconds, and reinsert it until you hear a click. If the chirping continues, the new battery itself may be defective—try a different battery from a different package. If a different battery stops the chirping, the first battery was faulty.

Can I use a rechargeable battery in my First Alert alarm?

No. First Alert alarms are designed for single-use alkaline batteries. Rechargeable batteries have a different voltage and may not power the alarm correctly. Always use a fresh alkaline 9-volt battery or the battery type specified in your manual.

What should I do with the old battery?

Do not throw it in the trash. Take it to a battery recycling program or a retailer that accepts used batteries—many hardware stores and electronics retailers have collection bins near the checkout. You can also search Earth911.com or Call2Recycle.org to find a drop-off location near you.

Does the alarm need to be unplugged before I change the battery?

No. Changing the battery while the alarm is powered on is safe. However, if your First Alert alarm is hardwired to your home's electrical system, it may have a backup battery in addition to the main power. In that case, the battery change will not affect the alarm's operation.