Test Hardwired Smoke and CO Alarms Before Heating Season

In Random Lake, Plymouth, Cedarburg, West Bend, and across our eight counties, late September is when the furnace starts getting real use again. That is also when hardwired smoke alarms and carbon monoxide alarms need a real check — not a glance at the ceiling on the way to the coffee pot.

Fuel-burning heat brings fire risk and carbon monoxide risk back into the house. Those alarms only help if they still power up, still interconnect, and still have a working backup battery when the lights blink out.

What USFA wants on the ceiling

The U.S. Fire Administration's smoke alarms page is clear about placement: smoke alarms inside and outside each bedroom or sleeping area, and on every level of the home, including the basement. Alarms should be interconnected so that when one sounds, they all sound. Mount them on the ceiling or high on the wall per the manufacturer.

USFA draws a hard line on hardwired work: only qualified electricians should install hardwired smoke alarms. Pulling a hardwired head, splicing a new interconnect, or adding a missing bedroom alarm on the house circuit is licensed electrical work — not a Saturday ladder project.

For hardwired alarms, USFA's care list is short:

1. Test every month.
2. Replace the backup battery at least once a year.
3. Replace the entire smoke alarm every 10 years from the manufacture date.

A hardwired alarm with a dead backup battery is half an alarm. When power dips during a fall storm, that backup keeps the horn alive.

Carbon monoxide before the furnace settles in

USFA's carbon monoxide page calls CO the “invisible killer” — colorless, odorless, and deadly when a furnace, heater, or generator is not working or vented right. More than 150 people in the United States die every year from accidental non-fire CO poisoning (CPSC figure cited by USFA).

Install CO alarms in a central location outside each separate sleeping area and on every level of the home. Keep dryer, furnace, stove, and fireplace vents clear. Portable generators stay outdoors, away from doors, windows, and vents.

The CPSC's cold-weather heating release says the same: smoke alarms on every level and inside each bedroom; CO alarms on every level and outside sleeping areas; battery power or battery backup; interconnected alarms preferred; test monthly; replace batteries yearly or use sealed 10-year units. NFPA's carbon monoxide safety guidance adds: choose a CO alarm with a recognized testing-laboratory label.

A five-minute check before first hard freeze

Walk the house once before the furnace runs every night:

1. Press Test on every smoke and CO unit. You want a full horn (and interconnect if the house is wired that way), not a weak chirp and silence upstairs.
2. Check the manufacture date. Smoke alarms past ten years get replaced, not cleaned and hoped.
3. Swap backup batteries on hardwired heads. Yearly swap is the USFA baseline even when house power was fine all summer.
4. Note missing rooms. A finished basement bedroom with no smoke alarm, or a level with no CO coverage, is a gap — not a January project.
5. Watch the furnace circuit. If heat start trips a breaker or the same run keeps tripping, write down what else was on and call. Do not upsize the breaker so the furnace “holds.”

Same fall season: outdoor receptacle covers before freeze, and garage loads on a real wall outlet.

Wisconsin code context

Wisconsin's electrical code update took effect September 1, 2026. The Department of Safety and Professional Services announced adoption of the 2023 National Electrical Code for new permitted work. Our Wisconsin NEC 2023 overview summarizes what that means at the house. New hardwired smoke or CO circuits and interconnects pull permits when your municipality requires them. More electrical safety tips for Wisconsin homes sit on the blog when you want the wider checklist.

When to call

Call us when a hardwired smoke or CO alarm will not test, when interconnect fails (one sounds and the rest stay quiet), when you need a licensed install or replacement on the house circuit, when backup-battery chirps will not clear after a fresh battery, or when the furnace circuit trips as heat season starts.

We are Monday through Friday, 8:00 a.m. to 4:00 p.m. After hours, call or message us and we will follow up when we open.

We are Couillard Electric LLC, based in Random Lake — your neighbors, not a franchise. Sheboygan, Ozaukee, Washington, Milwaukee, Waukesha, Fond du Lac, Calumet, and Manitowoc County. Call (262) 618-2851. For diagnostics, start at troubleshooting. For planned smoke, CO, or other residential circuit work, see residential electrical.