In this short video, Brian mounts a Kidde smart smoke alarm with a built-in indoor air quality monitor on a ceiling. Here is where alarms belong, how long they last, and what to know before you buy.

Video by Brian Huie on YouTube. Watch on YouTube

How often: Replace every 10 years
Video: 1 min 19 sec

Where should smoke alarms go?

Put a smoke alarm in every bedroom, outside each sleeping area and on every level of the home, including the basement. Large homes may need more.

Mount it on the ceiling or high on a wall, within 12 inches of the ceiling, and keep it at least 10 feet from the stove to cut down on false alarms.

Interconnected alarms are best: when one sounds, they all sound.

How long do smoke alarms last?

Replace every smoke alarm when it is 10 years old. Alarms with a 9-volt battery need a new battery at least once a year; alarms with a sealed 10-year lithium battery are replaced as a whole unit.

What does the alarm in the video do?

The Kidde model shown (P4010ACSAQ-WF) runs on 120-volt household power with a backup battery that lasts 10 years. It monitors indoor air quality, sends alerts to the Kidde app over Wi-Fi, and links with other hardwired Kidde alarms so that when one sounds, they all sound. It is a smoke alarm; for smoke and carbon monoxide in one unit, Kidde sells the P4010ACSCOAQ-WF.

Ionization or photoelectric?

The two sensor types detect different kinds of fires. The U.S. Fire Administration suggests having both types, or dual-sensor alarms.

Safety notes

Only a qualified electrician should install hardwired smoke alarms.
Never disable an alarm or pull the battery because cooking or a shower set it off. Open a window, press the hush button or fan the air instead.

Seattle-area notes

Washington law requires a working smoke alarm in homes that are sold. If a home has none, the seller must provide at least one before the buyer moves in.

The Seattle Fire Department installs free smoke and CO alarms for qualifying Seattle homeowners who are 65 or older, low income or living with a disability.

When to call a pro

Hire a licensed electrician for any hardwired alarm.

Sources

Checked October 2026. Manufacturer instructions for a specific model come first. General information, not a substitute for a licensed professional.

From the Home Care Manual by Brian Huie, a principal broker with Compass Real Estate in Seattle.

Home Care Manual

How to install a smart smoke detector (with air quality monitor)