Replace the battery in minutes by opening the alarm cover and sliding out the old cell

Most First Alert smoke alarms use a 9-volt battery that slides into a holder inside the unit. To change it, press the release button or tab on the side or bottom of the alarm cover—this varies by model—and gently pull the cover away from the mounting bracket. You'll see the battery holder with the old 9V battery inside. Slide the battery out, note which way the terminals face (the red and black wires or connectors), and slide the new 9V battery in the same direction. Push the cover back onto the bracket until it clicks. The alarm will usually chirp once to confirm the battery is seated correctly.

The whole job takes about two minutes. You do not need tools. The only thing that changes between First Alert models is where the release button sits and whether the battery holder is a clip or a socket, but the basic motion is the same: open, remove, replace, close.

Key Takeaways

  • First Alert smoke alarms hold a single 9-volt battery that you access by pressing a release button and pulling off the cover.
  • The battery slides into a holder inside the alarm; match the terminal direction of the old battery when you insert the new one.
  • A single chirp after you close the cover means the battery is installed correctly and the alarm is working.
  • If the alarm continues to chirp after you install a fresh battery, the unit itself may be at the end of its life and need replacement.
  • Test the alarm by pressing the test button on the cover after you finish; it should sound a loud alarm for a few seconds.

Locate the release button on your specific model

First Alert makes several alarm models, and the release button location differs. On many models, the button is on the side of the cover, marked with a small arrow or the word "Press." On others, it's on the bottom edge. Check the cover itself first—most have a small raised button or tab. If you don't see one when ready, look at the seam where the cover meets the mounting bracket and feel for a slight indent or ridge.

If you cannot find a release button, your model may use a twist-off cover instead. Grip the cover gently and turn it counterclockwise about a quarter turn; it should come free. Do not force it. If it does not budge after a gentle turn, stop and check the model number on the back of the unit, then search the First Alert website for your specific manual—it will show the exact release method.

Remove the old 9-volt battery safely

Once the cover is off, you will see the battery holder. It is usually a plastic clip or socket mounted inside the alarm body. The 9V battery sits in this holder with two wires or connectors attached—one red (positive) and one black (negative). Gently pull the battery straight out. Do not twist or rock it side to side; a straight pull is safest.

Set the old battery aside. You do not need to dispose of it when ready, but 9-volt batteries contain materials that should not go in regular trash. Most hardware stores and many retailers have battery recycling bins near the checkout. Keep the old battery in a safe place until you can drop it off.

Insert the new 9-volt battery in the correct direction

Before you touch the new battery, look at how the old one was oriented in the holder. The red wire or connector should attach to the positive terminal (usually marked with a + symbol), and the black wire to the negative terminal (marked with a − symbol). The battery itself has a small metal contact on top; this is the positive end.

Slide the new 9V battery into the holder in the same direction as the old one. The battery should fit snugly but not require force. If it does not slide in smoothly, you may have the polarity reversed—remove it and flip it 180 degrees. Once it is seated, you should hear or feel a small click as the connectors make contact with the battery terminals.

Close the cover and listen for the confirmation chirp

Align the cover with the mounting bracket and push it firmly back into place. You should hear a single chirp or beep—this is the alarm confirming that the battery is installed and the unit has power. If you hear nothing, open the cover again and check that the battery is fully seated in the holder. Push it in a bit further if there is any gap, close the cover, and listen again.

If the alarm still does not chirp after a second attempt, the battery may be dead or defective. Try a different new 9V battery. If a fresh battery still produces no chirp, the alarm unit itself may have failed and will need to be replaced.

Test the alarm to confirm it is working

After the cover is closed and you have heard the confirmation chirp, press and hold the test button on the cover. This button is usually in the center of the alarm face and is clearly marked "Test." Hold it for three to five seconds. The alarm should sound a loud, steady beep or wail. If it does, the unit is working correctly and your battery change is complete.

If the alarm does not sound during the test, open the cover again and double-check that the battery is fully inserted and the connectors are touching the terminals. If it still fails the test after you reseat the battery, the alarm unit has likely reached the end of its life. Most First Alert smoke alarms last 8 to 10 years; if yours is older than that, replacement is the safer choice.

When to replace the entire alarm instead of just the battery

If the alarm chirps constantly even after you install a fresh battery, or if it does not sound during the test, the unit itself is failing. A continuous chirp that does not stop after a few minutes usually means the alarm is at the end of its service life, not that the battery is bad. First Alert alarms are not repairable; they must be replaced as a whole unit.

You should also replace the alarm if it is more than 10 years old, regardless of whether the battery works. Smoke alarms lose sensitivity over time, and an old unit may not detect a fire reliably. Check the manufacture date on the back of the alarm; if it is more than a decade old, buy a new First Alert unit and install it in the same location using the same mounting bracket.

Frequently Asked Questions

What type of battery does a First Alert smoke alarm use?

First Alert smoke alarms use a standard 9-volt battery, often called a 9V or 9-volt cell. You can buy these at any hardware store, supermarket, or drugstore. They cost between two and five dollars each. Make sure you buy a fresh battery, not a used or old one, so the alarm will work reliably.

How often do I need to change the battery?

A 9-volt battery in a smoke alarm typically lasts six months to one year, depending on the alarm model and the battery brand. Most alarms will chirp once every 30 to 60 seconds when the battery is low, which is your signal to replace it. Do not ignore this chirp; it means the alarm no longer has enough power to detect smoke.

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

A continuous chirp after battery replacement usually means the alarm unit itself is failing, not the battery. It can also mean the battery is not fully seated in the holder. Open the cover, push the battery in firmly, and close the cover again. If the chirping continues, the alarm needs to be replaced.

Can I use a rechargeable 9-volt battery in my First Alert alarm?

Rechargeable 9-volt batteries are not recommended for smoke alarms. They lose charge faster than disposable batteries and may not provide enough power during a fire. Always use a fresh, disposable 9-volt battery. Your life depends on the alarm working when you need it.

What should I do with the old battery?

Do not throw a 9-volt battery in the trash. Take it to a hardware store, electronics retailer, or municipal hazardous waste facility that accepts battery recycling. Many stores have free battery recycling bins near the front entrance. Call ahead if you are unsure whether your local store accepts them.