Test every smoke detector and carbon monoxide detector in your home once a month, and replace the batteries at least once a year — many families tie this to a daylight-saving time change to make it easy to remember. The detectors themselves have a finite lifespan: smoke alarms should be replaced every ten years, and CO detectors every five to seven years (check the manufacture date stamped on the back of your unit). After ten years, the sensing elements in smoke alarms degrade and the unit may not respond reliably to actual smoke.

Why Monthly Testing Matters

Testing a detector takes about three seconds — press and hold the test button until the alarm sounds. If it chirps weakly or doesn’t sound at all, the battery is low or the unit has failed. A detector that looks fine on the wall and has never alarmed may have a dead battery or a failed sensing chamber. Monthly tests are the only way to know your detectors will work when they need to.

Colorado homes have an additional reason to be diligent: our high altitude and dry air mean combustion appliances like furnaces, water heaters, and fireplaces must work harder and are more prone to incomplete combustion under certain conditions. At 5,280 feet, appliances adjusted for sea-level operation can produce elevated carbon monoxide if they are not properly tuned for altitude. A functioning CO detector is a critical safety backstop for any home with gas appliances.

How Many Detectors Do You Need and Where Should They Go?

Colorado law requires smoke alarms on every level of the home, inside each bedroom, and outside each sleeping area. For carbon monoxide, CO detectors are required on each level and within fifteen feet of each bedroom door — particularly important in homes with attached garages, gas appliances, or any fuel-burning heating equipment. These are minimums; adding detectors in the kitchen (at least ten feet from the stove to prevent cooking-steam false alarms), laundry room, and attached garage provides better coverage.

Combination Alarms vs. Separate Units

  • Combination smoke/CO alarms are convenient and meet code requirements in most placements, but they have one significant drawback: if a combination unit reaches the end of its CO sensor life (typically five to seven years) but the smoke sensor is still functional, the entire unit needs to be replaced.
  • Separate dedicated units allow you to replace each on its own schedule, potentially saving money over time and ensuring you’re never running a degraded sensor longer than necessary.
  • Interconnected alarms — wired or wireless — are the safest configuration. When one alarms, they all sound simultaneously, giving every occupant the maximum amount of time to respond regardless of where in the home they are.

Hardwired vs. Battery-Only Detectors

Hardwired smoke detectors (which include a battery backup) are required in new construction and are more reliable than battery-only units because they continue operating even if the backup battery runs low during a power outage — when a fire or CO incident is more likely, not less. If your home has older battery-only detectors, upgrading to hardwired units with battery backup is a worthwhile investment. This work requires a licensed electrician to run wire and connect to your home’s electrical system.

The Connection Between CO Safety and HVAC Maintenance

Carbon monoxide in a home almost always comes from a combustion appliance — furnace, boiler, water heater, fireplace, or attached garage. A cracked furnace heat exchanger is one of the most serious and hardest-to-spot CO risks: the crack allows combustion gases to mix with the air being distributed through your ductwork. This is why annual furnace maintenance, which includes a heat exchanger inspection, is so important. A functioning CO detector is your warning system; annual HVAC service is your prevention strategy.

If your CO detector alarms, treat it as a real emergency: evacuate the home, leave the door open as you exit, and call 911 from outside. Do not re-enter until the fire department has cleared the home and identified the source. After any CO incident, have a licensed HVAC technician inspect every combustion appliance before operating them again.

For help upgrading your home’s detection system or inspecting your combustion appliances, Done’s electrical and HVAC teams can help. Explore our smart home and safety services, learn about electrical installation options for hardwired detectors, or schedule a furnace maintenance visit to verify your heating equipment isn’t contributing to CO risk.