Open the alarm and locate the battery compartment

Most First Alert smoke alarms have a battery compartment on the back or bottom of the unit. Look for a small door or panel that slides or twists open — you do not need tools. If your model is mounted on the ceiling, you may need to remove the entire alarm from its mounting bracket first by twisting it counterclockwise.

Once the compartment is open, you will see the old battery sitting in a plastic holder. The battery is usually a 9-volt rectangular battery, though some First Alert models use AA or AAA batteries instead. Check the label inside the compartment or on the back of the alarm to confirm which type yours uses.

Remove the old battery and note its orientation

Gently pull the old battery out of its holder. Before you discard it, take a moment to see which direction the terminals face — the positive and negative ends. Most battery holders have a small diagram showing which way the battery should sit, but if yours does not, remember that the red wire or clip usually connects to the positive terminal and the black wire to the negative.

If the battery is stuck, do not force it. Wiggle it gently side to side until it comes free. Some older First Alert models have batteries held in place with a clip or connector — if so, gently press or slide the clip away from the battery before pulling it out.

Insert the new battery in the correct direction

Slide or place the new battery into the holder, making sure the positive terminal faces the direction shown in the diagram or the direction the old battery was facing. For 9-volt batteries, the connector will only fit one way, so you cannot install it backwards. For AA or AAA batteries, align the flat end with the negative side and the bumped end with the positive side.

Push the battery in firmly until you hear or feel a click, which means the connector has made contact. If you do not hear a click, the battery may not be making a proper connection — remove it and try again, checking that the terminals are clean and the battery is fully seated.

Close the compartment and test the alarm

Slide or twist the battery compartment door closed until it clicks or sits flush against the alarm body. Do not force it — it should close smoothly. Once closed, press and hold the test button on the front of the alarm for three to five seconds. You should hear a loud beep or alarm sound, which means the battery is working and the alarm is functioning.

If you do not hear a sound, open the compartment again and check that the battery is fully seated and facing the correct direction. If the alarm still does not sound after reinserting the battery, the battery itself may be defective — try a different new battery from a different package.

Reinstall the alarm on its bracket if you removed it

If you took the alarm off the ceiling or wall to access the battery, line up the mounting slots on the back of the alarm with the bracket that is still attached to the wall or ceiling. Slide the alarm onto the bracket and twist it clockwise until it stops and sits snugly. You should feel resistance as you twist — do not force it past the point where it stops naturally.

Once the alarm is mounted, press the test button again to confirm it still sounds. A working alarm should produce a loud chirp or beep that lasts for several seconds.

Dispose of the old battery safely

Do not throw the old battery in the trash. Batteries contain chemicals that can harm the environment and should be recycled. Take the old battery to a local recycling center, an electronics retailer that accepts batteries, or a hazardous waste collection event in your area. Many hardware stores and Best Buy locations accept batteries for free recycling.

Check your city or county website for a hazardous waste drop-off location near you, or call your local waste management department to ask where batteries are accepted. Some retailers that sell batteries, including Home Depot and Lowe's, also have battery recycling programs at customer service desks.

Key Takeaways

  • First Alert smoke alarms typically use 9-volt, AA, or AAA batteries — check the label on your alarm to know which type to buy.
  • Open the battery compartment by sliding or twisting the door on the back or bottom of the alarm, and note which direction the old battery faces before removing it.
  • Insert the new battery in the same direction as the old one, push it in firmly until you hear a click, and close the compartment door.
  • Press the test button on the front of the alarm for three to five seconds to confirm the new battery is working and the alarm sounds.
  • Recycle the old battery at a local recycling center or retailer rather than throwing it in the trash.

Frequently Asked Questions

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

Check the label on the back of the alarm or inside the battery compartment door — it will say 9V, AA, or AAA. If you cannot find a label, look at the battery holder itself; the size and shape of the compartment will match the battery type. When in doubt, bring the alarm model number to a hardware store and staff can tell you which battery to buy.

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

A chirping or beeping sound every 30 to 60 seconds usually means the battery is low or not making good contact. Remove the battery, wipe the metal terminals with a dry cloth, and reinsert it firmly. If it still beeps, try a different new battery. If beeping continues after that, the alarm itself may be faulty and may need to be replaced.

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

Most First Alert models are designed for single-use alkaline batteries and do not work reliably with rechargeable batteries. Stick with new alkaline batteries — 9V, AA, or AAA depending on your model — to ensure the alarm functions when you need it.

How often should I change the battery?

Replace the battery once a year, or whenever the alarm chirps to signal low battery. Many people change batteries when they change their clocks for daylight saving time, which makes it easy to remember. Some newer First Alert models have 10-year sealed batteries that cannot be replaced — those alarms should be replaced entirely after 10 years.