Hardwired and interconnected smoke alarms: when you need an electrician

Updated November 10, 2026 · KeystoneProGuide editorial team

Why do smoke alarms belong in a guide about electricians?

Because one kind of smoke alarm is part of the house wiring. The U.S. Fire Administration explains that smoke alarms are powered either by a battery or by the home's electrical system, and that the second kind, called hardwired, usually also has a backup battery. It says plainly that only qualified electricians should install hardwired smoke alarms.

Battery alarms are a homeowner's job, and the Fire Administration notes that some fire departments will install battery-operated alarms at no cost. Hardwired alarms, and adding new ones to the wiring, are an electrician's.

How much difference do working alarms make?

A large one, on the National Fire Protection Association's figures. It says roughly three out of five home fire deaths happen in homes with no smoke alarms or no working ones, and that the risk of dying in a home fire is cut in half in homes with working smoke alarms.

What does "interconnected" mean?

That when one alarm sounds, they all sound. The Fire Administration says to choose interconnected alarms, and the NFPA says it is best to use them. The Consumer Product Safety Commission says interconnected alarms are best for carbon monoxide too.

Interconnection does not always mean new cable. The Fire Administration also describes radio-frequency, or wireless, alarms that communicate from one to the next without wires, which it prices from $40 and up. If you are adding alarms to a finished house, ask the electrician whether wired or wireless interconnection suits it.

Where should alarms go?

The bodies agree on the pattern:

• Inside every bedroom. The Fire Administration, the NFPA and the CPSC all say so.
• Outside each sleeping area. In the hallway or space outside the bedrooms.
• On every level of the home, including the basement, which the NFPA and the Fire Administration name specifically.
• High up. The Fire Administration says to put alarms on the ceiling or high on the wall, following the manufacturer's instructions.

For carbon monoxide, the CPSC says to install alarms on each level and outside separate sleeping areas, and the Electrical Safety Foundation, a nonprofit safety group, says the same in its generator safety advice.

What about someone who cannot hear an alarm?

There are alarms for that. The Fire Administration says alarms for people with hearing loss may have strobe lights that flash, or that vibrate, to alert people who cannot hear a standard alarm. If a household member is deaf or hard of hearing, raise it when you plan the job, since such devices still need to be placed and, where hardwired, connected like any other alarm. The Fire Administration also notes that a closed bedroom door may slow the spread of smoke, heat and fire, one reason it wants an alarm inside each bedroom as well as outside.

Which type of sensor should you choose?

Both kinds, or a dual sensor. The Fire Administration says there are two basic types, ionization and photoelectric, that they detect different kinds of fires, and that because no one can predict which kind will start, every home should have both types or dual-sensor alarms containing both. It adds that your city, county or state may require a particular type, and to ask the local fire marshal.

The Fire Administration lists typical prices: ionization or photoelectric alarms from $6, dual-sensor from $24, alarms with a microprocessor from $30 and wireless interconnected alarms from $40. An electrician's charge for installing hardwired alarms is on top of that.

Does adding hardwired alarms need a permit?

Running new wiring for alarms is added wiring, which Pennsylvania's code regulation says is not an ordinary repair, so expect a permit where new circuits or cables are involved. Ask your code office how it treats replacing existing hardwired alarms. Some municipalities have their own paperwork: Haverford Township in Delaware County, for example, lists a smoke detector affidavit among its forms.

How do you look after them?

The Fire Administration's schedule depends on the power source:

It says smoke alarms need replacing 10 years from the date of manufacture. The CPSC says never to ignore an alarm: get outside immediately and call 911.

What should you ask the electrician?

• Can the new alarms be interconnected with the existing ones, by wire or wirelessly?
• Will every bedroom, every level and the basement be covered?
• Will you include carbon monoxide alarms on each level?
• Does the job need a permit here, and will you apply for it?
• What is the manufacture date on the alarms you are fitting?

Which smoke-alarm tasks are yours and which are not is in doing it yourself or hiring, the testing and replacement calendar sits with other checks in how often to check, and prices for common jobs are in the cost guide. Electricians are listed on the electricians directory page.

Sources

1. Smoke Alarms, U.S. Fire Administration
2. Learn More About Smoke Alarms, National Fire Protection Association (NFPA)
3. Winter Storm May Knock Out Power; CPSC Warns of Deadly Carbon Monoxide and Fire Risks, U.S. Consumer Product Safety Commission
4. Generator Safety, Electrical Safety Foundation International (ESFI)
5. Home Electrical Fires, Electrical Safety Foundation International (ESFI)
6. Building & Codes Department, Township of Haverford
7. 34 Pa. Code § 403.62. Permit requirements and exemptions., Commonwealth of Pennsylvania (Pennsylvania Code)