First Alert BRK SC-9120B Hardwired Smoke and Carbon Monoxide Alarm (SC9120BFF)

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WHAT'S INCLUDED:

• Operating instructions/Owner's Manual

• Mounting Base

• Smoke Alarm and Carbon Monoxide Detector

• Wires (to connect smoke alarm to house wiring

• Dust Cover (to preserve the smoke alarm should you do a home renovation, for instance)

DO SMOKE ALARMS EXPIRE OR NEED TO BE REPLACED?
I have several First Alert smoke alarms in my house that were set to expire in a couple months. I read many different sources on smoke alarms as well as industry guidance on replacing smoke alarms. It's widely recommended to replace smoke alarms every 10 years and carbon monoxide detectors every 5 years. According to the National Fire Protection Association (NFPA):

Almost one in five Americans who have smoke alarms (19 percent) say the oldest smoke alarm they currently have in their home is 10+ years old.

Nearly one in five Americans who have smoke alarms (18 percent) are not at all sure how old the oldest smoke alarm they currently have in their home is.

When asked how often they should replace smoke alarms, nine in 10 Americans (90 percent) did not select the correct answer, which is once every 10 years.

FEATURES OF THE BRK SC-9120B MODEL:

I went with this model from First Alert, because:

• Fit preexisting mounting brackets in my home (First Alert)

• I haven't had any trouble with the ones currently in my home

• I wanted to add carbon monoxide detection. 

• Interconnected - this smoke alarm can connect with your other hardwired smoke alarms. 

IONIZATION VS PHOTOTELECTRIC SMOKE ALARMS:

This particular smoke alarm has an ionization sensor. Ionization sensors are generally cheaper, but there are pros and cons to an ionization sensor compared to a photoelectric sensor. In short, they are designed to detect different types of fires quickly. The NFPA describes the benefits/drawbacks of each type below:

Ionization smoke alarms are generally more responsive to flaming fires. Ionization-type smoke alarms have a small amount of radioactive material between two electrically charged plates, which ionizes the air and causes current to flow between the plates. When smoke enters the chamber, it disrupts the flow of ions, thus reducing the flow of current and activating the alarm.

Photoelectric smoke alarms are generally more responsive to fires that begin with a long period of smoldering (called “smoldering fires”).  Photoelectric-type alarms aim a light source into a sensing chamber at an angle away from the sensor. Smoke enters the chamber, reflecting light onto the light sensor; triggering the alarm.

It's widely recommended that you have both types of smoke alarms, photoelectric and ionization, in your home. Having each will help to more rapidly detect fires.

CONCLUSION:

I've have had these units in my home for several months at the time of this writing and the First Alert smoke alarms prior to these units for almost 10 years. I haven't had any issues at all with them. Please remember to replace your units, whether with this model or any other, within 10 years (5 years for carbon monoxide units).

NFPA Source: Photoelectric vs Ionization
NFPA Source: How Often to Replace Smoke Alarm?