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Long Life Battery Smoke Alarm

The First Alert Long Life Battery Smoke Alarm features an extended long-life lithium battery that is warranted by the manufacture to ensure a decade's worth of protection! This effectively translates to ten years of constant and undisturbed coverage. Utilizing an Ionization Sensor, this alarm is especially effective in recognizing smoke brought on by flaming fires. This alarm comes equipped with a Mute Button that serves the dual purpose of quickly silencing your alarm as well as testing its function. First Alert's Long Life Battery Smoke Alarm also features an EZ access battery door that removes the hassle and burden of collecting your alarm from the ceiling and replacing its batteries. This alarm carries a 10-year limited warranty and meets UL217 Standards.

Ionization Sensor Reliably Detects Flaming Fires

The First Alert Long Life Battery Smoke Alarm comes equipped with an ultra-reliable ionization sensor to provide the earliest possible warning of a fast-flaming fire. The sensor is optimized to detect flaming fires, such as those caused by paper, kitchen grease, and other fast-combusting materials.

Battery-Powered Alarm Installs Easily

This battery-powered smoke detector requires no rewiring and no electrician to install. Simply mount it on a wall or ceiling using the open mounting design. An end-of-life signal will notify you when the detector is nearing expiration.

Test and Silence Button

Mute Button has been included to serve the dual purpose of silencing nuisance alarms and testing the functionality of your alarm.

First Alert Long Life Battery Smoke Alarm SA305CN3

* California and New York Residents - Please note this alarm is not compliant with your State's 10 Year Sealed Battery Alarm Legislation Requirements.

How often do you need to change the batteries?
Actual battery service life depends on the particular design of your smoke or carbon monoxide alarm and the environment in which it is installed. All kinds of alarm batteries specified in the user's manual are acceptable replacement batteries. Regardless of the manufacturer's suggested battery life, you MUST replace the batteries immediately once the unit starts "chirping" (the "low battery warning"). It is recommended that you change the batteries in your alarms when you change your clocks for daylight saving time. Also consider replacing your current alarms with 10-Year Life Alarms that never require a costly battery replacement for the ten year life of the alarm. This 10-Year series is available in smoke, carbon monoxide and combination alarms.

What is the proper placement of smoke alarms?
It is important that you have the proper placement for your smoke alarms. Install your alarms at least 20 feet from appliances like furnaces and ovens, which produce combustion particles. Alarms should be at least 10 feet from high humidity areas like showers and laundry rooms, and at least 3 feet from heat/AC vents. Be sure to install a smoke alarm in each bedroom, one at the top of each stairwell, and one on every level.
My smoke alarm keeps chirping and beeping. Why does my smoke alarm chirp intermittently?
It is likely that the reason your smoke alarm keeps chirping and beeping is that the battery is low. Whenever your smoke alarm keeps chirping, replace the battery immediately.

Other reasons include: It could be a different device or appliance such as a security system, monitor, carbon monoxide alarm, or other device which has a similar low battery or alert signal. Some of the same factors that cause unwanted alarms can cause intermittent alarms: dust and insects in the alarm or power interruptions in hardwired alarms. Improper wiring on AC or AC/DC smoke alarms. AC alarms will chirp every 5 seconds if the interconnect wire is grounded. The orange interconnect wire should NEVER be grounded; it should only be used to interconnect other smoke alarms or compatible devices.

Why doesn't my smoke alarm sound when I push the test button?
It is important that you frequently test your smoke alarms. When you are testing your smoke alarm, there are a number of reasons why the alarm might not sound:
  • You may not be holding the test button down long enough. Try holding it down for up to 10 seconds (20 seconds on photoelectric models) .
  • Your battery may not be installed properly or snapped all the way in place. Even if the alarm sounded briefly when the battery touched the terminals, you still need to make sure it is snapped securely in place. If the battery is loose, in cannot power the smoke alarm properly. After installing new batteries, be sure to test your smoke detector.
  • Your AC power may not be on. AC and AC/DC units will have a power indicator light (red or green) that shines continuously when they are receiving electrical power.
  • If you have a 10-Year model, the smoke alarm may not have been properly activated. If the tab broke away before the alarm was activated, you can use a toothpick to move the switch over to test the alarm.
Why does my smoke alarm go off when I install a battery or turn on the AC power?
It is normal for smoke alarms to go off and sound briefly (up to 5-10 seconds) when you install a new battery or when they are powered up. If the alarm continues to go off and no smoke is present, the cause may be one of the following:
  • There may be insufficient battery power, try new batteries.
  • Problems with voltage or insufficient electrical power (brown out) may cause a continuous weak sounding alarm. For AC or AC/DC models, temporarily disconnect power at the service panel until the brown out is over. If you do not restore the AC power, your smoke alarms cannot warn you of a fire.
  • Incompatible warning device. If an incompatible alarm or auxiliary device is linked into a series of AC or AC/DC smoke alarms it may cause the system inadvertently go off.
My smoke alarm keeps chirping, even with a new battery. What is causing this?
There are a number of possible causes for your smoke alarm to keep chirping even with a new battery.
  • It is possible that your smoke alarm "silence" button was pushed by mistake. The alarm will now "chirp" once a minute for up to 15 minutes before resetting.
  • Are you sure it's the smoke alarm? Funny to ask, but other devices have similar low battery chirps or warning tones.
  • Your "new" batteries may not be fresh. If batteries are stored, especially in cold areas like refrigerators, they lose their charge more quickly. Always check the freshness date on the package when buying new batteries. Keep plenty of replacement batteries on hand so that you are sure to always be protected by your smoke alarms.
I lost my First Alert smoke alarm owner's manual. How can I get a new one?
First Alert smoke alarm owner's manuals are available online for download at no cost. Find your alarm in our Smoke Alarms section.
Why does the National Fire Protection Association (NFPA) recommend that home smoke alarms be replaced after 10 years?
Smoke alarms have a limited life. Although each smoke alarm and all of its parts have passed many stringent tests and are designed to be as reliable as possible, any of these parts could fail over time. Therefore, you must test the devices weekly. The unit should be replaced immediately if it is not operating properly. The performance of smoke alarms older than 10 years is simply not reliable. To ensure your family's safety, all carbon monoxide and smoke/CO combination alarms need to be replaced every 5-7 years. All smoke alarms need to be replaced every 10 years.

If it's time to replace your alarms, consider the NEW 10-Year Life series and never have to worry about a battery replacement for the life of the alarm.10-Year alarms are available in smoke, carbon monoxide and combination alarms.

Product Details
Product Specs
Smoke Alarms and Smoke Detectors
Product Manuals

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SA305CN3 customer reviews

Overall Rating

48 Reviews
48 customers recommend this product
First Alert SA305CN3 Long Life Battery Smoke Alarm (1039815) Reviews
Edward Davis
October 28, 2020
Verified Purchase
Excellent bare-bones smoke detetor

Very happy with this smoke detector. Cost-effective, simple, and reliable.

Mark Andresky
October 7, 2020
Verified Purchase
Easy to Install & Great Performance

We have been buying this brand and model for many years. They almost always last 8 - 10 years on the original lithium ion battery, are very easy to install, and don't produce the false alarms that so many detectors do.

Mark Andresky
April 5, 2020
Verified Purchase
One of the Best Household Smoke Detectors Out There

This basic smoke detector with a long life lithium ion battery is the only one we use in almost every room of our house. It's very affordable. We've been getting 8 - 10 years of life from the lithium ion batteries. The units almost never produce a false alarm beeping for something other than a true fire. They are also small and inconspicuous when installed, blending into the white ceiling. Will continue to purchase as long as First Alert makes them!

Mark Andresky
November 5, 2019
Verified Purchase
Excellent Long Term Performance

I have been buying this model for many years for my home and as gifts for the homes of family members. It is very easy to install, and the long life battery lasts many years 7 - 9 yrs in my experience, reducing the annoyance of changing batteries frequently.

Scott Martin
June 17, 2019
Verified Purchase
Great value

I found this alarm to be an excellent value. The long-lasting battery easily compensates for the few extra dollars you'll pay over an alarm with a regular 6 month - 1 year battery.

Rose Frohlich
January 29, 2019
Verified Purchase
First Alert Long Life Battery Smoke Alarm

Works great! I really like the 10 year lit-hon battery.

Mark Andresky
November 28, 2018
Verified Purchase
Well Designed & Reliable

We have been installing this model in most rooms of our home for many years--always reliable, easy to install, and usually lasts the full 10 years. Very economical as well compared to comparable models from other brands.

Linda Guillermo
May 15, 2018
Verified Purchase


Mark Andresky
May 4, 2018
Verified Purchase
Well Designed & Reliable

Have used this model throughout our home for many years. Reliable and easy to install. Small, unobtrusive design makes it less noticeable compared to competitive models.

Cheryl Kucer
February 8, 2017
Verified Purchase
Finally! Long life batteries

Tried to get these at local hardware stores & could only get three. So I went on first alert website, found the rest that I needed and ordered them. Prices were better than hardware store, easy to order and I got them right away. Very, very happy with first alert.

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