Smoke Detector & Carbon Monoxide Alarm Buying Guide

Smoke and flames from a fire are easy to see, but a fire that begins in a vacant part of the house or starts in the middle of the night can spread undetected. Once a fire starts, it can grow quickly.

Carbon monoxide (CO) poses an invisible threat. It’s a colorless, odorless gas produced by any fuel-burning appliance or fixture, such as a furnace, water heater or fireplace. Carbon monoxide can build up in the home from malfunctions or improper venting in these devices. It can also accumulate if the home is sealed for energy efficiency, reducing the exchange of inside and outside air. An attached garage in which a vehicle is running can also allow carbon monoxide to enter the home. The gas is dangerous because it replaces the oxygen in the air and, when inhaled, creates a toxic compound in your body. For more on carbon monoxide, see the Centers for Disease Control and Prevention’s carbon monoxide poisoning information.

A carbon monoxide fire alarm can help you protect your home and family from these threats, even when they occur in remote areas of the home or at night when everyone is asleep. You can purchase the devices separately or as combination units.

There are carbon monoxide alarms and smoke detectors that are hard-wired models. They connect to your home wiring or battery-operated models. Carbon monoxide alarms are also available as models that plug into home electrical outlets. Look for battery backup capability in devices that run off of a home electrical system to keep the unit functioning during a power outage. Some smoke detectors, fire detectors and carbon monoxide alarms feature built-in power cells that are designed to last the life of the device.

The life span of smoke detectors, carbon monoxide alarms and combination units differ based on factors such as device type, model and where they’re installed. See the manual for specific information on when to replace a unit. In general, replace a smoke detector after no more than 10 years and a carbon monoxide alarm after no more than five years. Combination-unit life span typically ranges between five and seven years. If a device indicates an end-of-life condition, replace it immediately.

• Photoelectric and ionization sensors are two sensor types for smoke detectors. Photoelectric smoke detectors are typically more sensitive to particles generated by fires that smolder, such as those ignited by a cigarette in a bed or upholstery. Ionization smoke detectors tend to be more sensitive to particles generated by flaming fires, such as burning paper or grease. You can find smoke detectors that use one or the other type of sensor and some that use both. Smoke detectors that also function as carbon monoxide alarms will only have one type of smoke sensor. For protection against both types of fires, install ionization and photoelectric smoke detectors or detectors that use both types of sensors.
• Voice notification on carbon monoxide alarms and combination units lets you program the location of the device from preset selections. When the alarm sounds, the voice warning indicates the location and, for combination units, the type of threat detected.
• A linking feature allows you to connect compatible units so all linked units sound an alarm when one detects a threat. This functionality can warn of hazards in remote areas of the house. If you install units that link wirelessly, pay attention to the range and placement restrictions for the linking feature.
  Home-management-system compatibility lets you connect the device to some home-management systems to send mobile alerts when the alarm activates.
  
• A silencing feature allows you to temporarily stop an unwanted alarm for a specific time period.
• Audible status alerts, such as low battery and end of life, let you know when the device needs attention.
• A display screen shows status information, such as battery level, low battery and end of life for the device. When a carbon monoxide alarm sounds, some models display the carbon monoxide level recorded and, for combination units, the threat type. Some carbon monoxide alarms also display peak carbon monoxide levels recorded over a specific period of time.
• Smart smoke detectors are connected to the internet and offer fire protection through an app on your smartphone or another smart device, so you get alerts about an emergency whether you’re home or away.

  Low-profile models, microdesign models and finish options allow the device to blend in with your home décor.
  

Follow the manufacturer’s instructions for the correct smoke and carbon monoxide detector placement. Locations include:

• Each floor of the home
• Each bedroom
• Each hallway close to sleeping areas — if a hallway is longer than 40 feet, place devices at both ends
• The top of the stairway
• The bottom of the stairway leading to the basement
• Each living area

Check your manual for installation locations to avoid and information on how far to install the devices from furnaces, heaters, stoves, water heaters, and other appliances and fixtures.

See Install a Smoke and Carbon Monoxide Alarm to learn general steps for installing the best battery smoke detector and carbon monoxide alarm for your home.

If your smoke or carbon monoxide detector is going off regularly when there are no signs of a fire or a carbon monoxide threat, it could be due to one of the following reasons:

• The battery might be loose, dying or installed incorrectly. Inspect it and check the use-by date.
• The alarm sensors may be dirty. Try wiping down the alarm and make a habit of dusting it every time you test it or change the battery.
  
• The unit may be installed near an open window or air vent. A draft can blow dust or pollen into the alarm sensors.
  
• The humidity in the area near the alarm may be too high. Steam from a hot shower can trigger an alarm if it’s too close to the bathroom.
  
• Your detector may be too close to cooking equipment. Steam or smoke from cooking or a burst of heat from an open oven door can trigger a smoke alarm if it’s too close to the stove. Check the instructions for recommended positioning.
  
• Your detector may need to be replaced. Review the user manual to see how many years your detector is meant to last. If you need a new one, check out our recommended carbon monoxide alarms and smoke detectors.
  

If your carbon monoxide or smoke alarm keeps beeping sporadically, check the instructions to see what each specific beep pattern means. This will vary by manufacturer and detector model, but here are some common alert examples and their meanings:

• One beep every 30 or 60 seconds could mean the battery needs to be changed or might be installed incorrectly.
  
• Several beeps per minute might indicate the detector is old and needs to be replaced.
• Multiple, consistent beeps followed by a short pause means a threat has been detected.

To stop your detector from chirping due to a battery issue, check the manufacturer’s instructions for the battery type and installation details. Although the instructions may vary slightly by model, here's how to change a smoke detector battery in three simple steps.

Make sure you and your family are familiar with the smoke detectors and carbon monoxide alarms in your home:

• Learn the available features and how to use them.
• Understand how the units respond to threats so you can quickly interpret alarms.
• Learn how the device indicates situations, such as loss of power, low batteries and end of life.
• Know the life span and initial power-up date of each unit and replace units at the proper time. Some units alert you when they reach the end of their life span.
  
• After an alarm, follow the manufacturer’s instructions for resetting or replacing your device.