What is a smoke detector?

A smoke detector senses airborne particles and sounds an alarm to warn of fire; home units are also called smoke alarms. Some alarms use flashing lights or vibration for people with hearing loss. USFA warns that a sounding alarm may leave less than 2 minutes to get everyone outside, so plan for an alert everyone can perceive.

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By InstaBids editorial team with AI research agents. Updated 2 November 2026

What this means for your home project

Compare your alarm’s manufacture date with USFA’s 10-year replacement point; plan to replace the unit when it reaches that age. Source: U.S. Fire Administration, read 2026-11-02.
Read the manufacturer’s placement instructions for your alarm model before choosing its location. Source: U.S. Fire Administration, read 2026-11-02.
Ask for a written installation scope listing alarms in every bedroom, outside each separate sleeping area and on every level, including the basement; the reply should identify the proposed locations. Source: U.S. Fire Administration, read 2026-11-02.
For hardwired installation, ask for written confirmation that a qualified electrician will perform the work. Source: U.S. Fire Administration, read 2026-11-02.

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What types of smoke alarms can I buy?

The two basic sensor types are ionization and photoelectric. Ionization tends to respond faster to flaming fires; photoelectric tends to respond faster to smoldering fires, which burn slowly. USFA recommends having both technologies, either in separate alarms or together in a dual-sensor alarm. Choose the sensing technology as well as the power supply. “Ionization smoke alarms tend to respond faster to the smoke produced by flaming fires than photoelectric smoke alarms.” Source: U.S. Fire Administration, read 2026-11-02. “Photoelectric smoke alarms tend to respond faster to the smoke produced by smoldering fires than ionization smoke alarms.” Source: U.S. Fire Administration, read 2026-11-02. “Because both ionization and photoelectric smoke alarms are better at detecting distinctly different yet potentially fatal fires, and because no one can predict what type of fire might start in a home, the USFA recommends that every home and place where people sleep be equipped with either (a) both ionization and photoelectric smoke alarms, or (b) dual sensor smoke alarms (which contain both ionization and photoelectric smoke sensors).” Source: U.S. Fire Administration, read 2026-11-02.

What powers a smoke alarm?

Battery-powered alarms can use a disposable 9-volt battery or a nonreplaceable 10-year battery. Hardwired means powered by the home’s electrical system; USFA says these alarms usually also have a backup battery needing yearly replacement. A long-life battery and a hardwired supply are different arrangements, so identify the power type before planning maintenance. “If the smoke alarm is powered by battery, it runs on either a disposable 9-volt battery or a nonreplaceable 10-year lithium-ion (“long-life”) battery.” Source: U.S. Fire Administration, read 2026-11-02. “Alarms that get power from your home's electrical system, or “hardwired” alarms, usually have a backup battery that will need to be replaced once a year.” Source: U.S. Fire Administration, read 2026-11-02.

Where do I put smoke alarms in my home?

USFA recommends alarms in every bedroom, outside each separate sleeping area and on every level, including the basement. Interconnected means that when one sounds, they all sound. For an installation bid, ask for a written list of these alarm locations and whether the alarms will be interconnected. USFA says only qualified electricians should install hardwired alarms. “Installing smoke alarms in every bedroom, outside each separate sleeping area, and on every level of a home — including the basement — is a fire safety precaution that all homeowners and landlords in your community need to take to protect residents from fire.” Source: U.S. Fire Administration, read 2026-11-02. “Choose interconnected smoke alarms so that when one sounds, they all sound.” Source: U.S. Fire Administration, read 2026-11-02. “Only qualified electricians should install hardwired smoke alarms.” Source: U.S. Fire Administration, read 2026-11-02.

How do I take care of my smoke alarm?

Test smoke alarms monthly. USFA says to replace 9-volt batteries at least yearly and to replace alarms 10 years from their manufacture date. Its guidance also says to follow the manufacturer’s instructions for replacing the entire alarm with a nonreplaceable long-life battery. Replacing a removable battery and replacing an aging alarm are separate tasks. “Test smoke alarms every month and replace 9-volt smoke alarm batteries at least once every year.” Source: U.S. Fire Administration, read 2026-11-02. “They need to be replaced 10 years from the manufacture date.” Source: U.S. Fire Administration, read 2026-11-02. “Replace the entire smoke alarm according to the manufacturer's instructions.” Source: U.S. Fire Administration, read 2026-11-02.

What should I do if my smoke alarm sounds while I'm cooking?

For a cooking nuisance alarm, USFA says to leave the battery in place, open a window or door and press the hush button. NIST explains that particles from cooking food can trigger alarms even without burnt food. This advice concerns a known cooking nuisance: USFA warns that a sounding smoke alarm may leave less than 2 minutes to get everyone outside safely. “Never take the battery out of your smoke alarm while cooking!” Source: U.S. Fire Administration, read 2026-11-02. “Open a window or door and press the “hush” button.” Source: U.S. Fire Administration, read 2026-11-02. “Smoke alarms near kitchens can detect the particles coming off your food as it cooks, even if you don’t burn it.” Source: National Institute of Standards and Technology, read 2026-11-02. “When you hear a smoke alarm, you may have less than 2 minutes to get everyone outside and safe.” Source: U.S. Fire Administration, read 2026-11-02.

How do smoke detectors work?

Ionization detection uses electrically charged air between two metal plates; smoke particles reduce the current. Photoelectric detection instead senses light reflected from particles inside a chamber. NIST explains both mechanisms below. These are two ways of sensing airborne particles, rather than two different ways of supplying the alarm with power. “These use a small bit of safely shielded radioactive material that electrically charges, or ionizes, the air molecules between two metal plates.” Source: National Institute of Standards and Technology, read 2026-11-02. “When particles enter the chamber, they attract the ions and carry them away, reducing the current.” Source: National Institute of Standards and Technology, read 2026-11-02. “This technology works by detecting light that is reflected off particles from a light beam inside the sensing chamber.” Source: National Institute of Standards and Technology, read 2026-11-02.

Sources

Smoke Alarms — U.S. Fire Administration; read 2026-11-02.
Position Statements: Home smoke alarms — U.S. Fire Administration; read 2026-11-02.
How Do Smoke Detectors Work? — National Institute of Standards and Technology; read 2026-11-02.