How to Change the Battery in a First Alert Smoke Detector

The basic steps to replace your First Alert battery

Most First Alert smoke detectors use a 9-volt battery that you can swap out in under a minute. Open the detector by twisting the cover counterclockwise or pressing the release tab on the side — the method depends on your model, but both are marked on the unit itself. Once the cover comes off, you will see the battery connector, a small plastic clip holding the battery in place. Disconnect the old battery by pulling the connector away from the battery terminals, then insert the new 9-volt battery into the connector and push it back onto the battery inside the detector. Close the cover by twisting it clockwise until it clicks, then press the test button to confirm the detector is working.

The test button is usually on the front or bottom of the detector. When you press it, you should hear a loud alarm for a few seconds. If you hear nothing, the battery may not be seated correctly — open the cover again and make sure the connector is fully pushed onto the battery terminals. If the alarm still does not sound, the new battery itself may be defective, so try a different one.

Key Takeaways

First Alert detectors typically use a standard 9-volt battery that you can buy at any drugstore or hardware store for a few dollars.
The cover twists counterclockwise or has a release tab; check the markings on your specific model to know which method to use.
After inserting the new battery, always press the test button to make sure the detector is working before you close it up.
If the alarm does not sound after a battery change, reseat the battery connector or try a fresh battery, because a loose connection or defective battery is the most common cause.
Replace the battery once a year or whenever the detector chirps — a chirp every 30 to 60 seconds means the battery is low.

When your First Alert detector chirps instead of alarming

A chirp every 30 to 60 seconds is the detector telling you the battery is running low. This is not an emergency, but it means you should change the battery within the next few days. The chirp will continue until you replace it, and it will get louder and more frequent as the battery drains further.

Some First Alert models have a low-battery indicator light that flashes at the same time as the chirp. This light is usually red or amber and sits on the front of the detector. The chirp and light both stop as soon as you insert a fresh battery and close the cover.

Which battery type to buy for your First Alert detector

First Alert makes detectors that use either a 9-volt battery or two AA batteries, depending on the model. Check the inside of your detector cover or the back of the unit — the battery type is printed there. If you see "9V" or "9 Volt", buy a standard 9-volt battery. If you see "AA", buy two AA batteries.

You do not need a special brand. Any 9-volt or AA battery from a drugstore, grocery store, or hardware store will work. Alkaline batteries (the standard kind) last longer than carbon-zinc batteries, so they are the better choice. Rechargeable batteries are not recommended for smoke detectors because they lose charge faster and may not power the alarm when you need it.

How often to replace the battery

Change the battery in your First Alert detector at least once a year, even if it has not started chirping. Many people change their batteries on the same day they change their clocks for daylight saving time — that way you remember to do it twice a year. If your detector chirps before a year has passed, change the battery right away.

Some First Alert detectors have a 10-year sealed battery that cannot be replaced. These units have a date printed on the back. When that date arrives, you must replace the entire detector, not just the battery. If you are not sure whether your detector has a replaceable battery, open the cover and look inside — if you see a battery, it is replaceable; if you see only wires, it is sealed.

Troubleshooting a detector that still does not work after a battery change

If you have inserted a fresh battery, pressed the test button, and heard nothing, first make sure the battery connector is fully seated. Open the cover again and look at where the connector clips onto the battery. The connector should be pushed all the way down so the metal contacts touch the battery terminals. If there is a gap, push it down until you hear a click.

If the connector is seated and the alarm still does not sound, try a different new battery. The battery you inserted may be defective — this happens occasionally, especially with older stock. If a second battery also produces no sound, the detector itself may have failed. First Alert detectors typically last 10 years, so if yours is older than that, replacement is the next step.

Do not assume the detector is broken if the test button produces only a quiet beep instead of a loud alarm. Some First Alert models have a quieter test mode to avoid startling you. Read the instructions on the back of the detector or on the inside of the cover to see what the test button is supposed to sound like on your specific model.

Where to position your detector after changing the battery

The battery change itself does not affect where the detector should sit, but it is a good time to check the placement. First Alert recommends mounting detectors on the ceiling or high on a wall, at least 4 inches away from corners and light fixtures. Smoke rises, so a detector near the floor will not catch smoke as quickly as one near the top of the room.

Install one detector on every level of your home, including the basement. If you have a hallway, put one there too. Bedrooms should have a detector inside the room or just outside the door so you hear the alarm while sleeping. Keep detectors away from kitchens and bathrooms, where steam and cooking smoke will trigger false alarms.

Frequently Asked Questions

Can I use a rechargeable battery in my First Alert smoke detector?

Rechargeable batteries are not recommended for smoke detectors. They lose their charge faster than alkaline batteries and may not have enough power to sound the alarm when you need it most. Stick with standard alkaline 9-volt or AA batteries.

What should I do with the old battery after I remove it?

Take the old battery to a recycling center or a store that accepts battery recycling, such as Best Buy or Home Depot. Many drugstores also have battery recycling programs. Do not throw batteries in the trash — they contain materials that can harm the environment.

Why does my detector still chirp after I put in a new battery?

The battery connector may not be fully seated. Open the cover and push the connector down until it clicks. If the chirp continues after you close the cover, try removing the battery, waiting 30 seconds, and reinserting it. If the chirp still does not stop, the detector itself may have a fault and may need to be replaced.

How do I know if my First Alert detector has a replaceable battery or a sealed battery?

Open the cover and look inside. If you can see a battery, it is replaceable. If you see only wires and no battery compartment, it has a sealed 10-year battery. Sealed-battery detectors have an expiration date printed on the back — when that date arrives, replace the entire unit.

Is it normal for the detector to alarm when I press the test button?

Yes. The test button is designed to trigger the alarm so you can confirm the detector is working. The alarm should sound for a few seconds and then stop. If nothing happens, the battery may not be connected properly or the detector may have failed.

This guide is for general information only and is not medical, financial, legal, or other professional advice. For decisions specific to your situation, consult a qualified professional. See our Editorial Policy.