Want to sleep better? Get yourself a new smoke detector and CO alarm.

House fires can happen to anybody at any time, but they occur most often in the winter, when people are using heating equipment, fireplaces, and space heaters. And carbon monoxide poisoning often occurs when people are asleep. Because of the colorless and odorless nature of the gas, many don't realize they are being poisoned.

That's why you'll probably sleep more soundly knowing you have installed smoke detectors and CO alarms. People without functioning smoke alarms are almost nine times more likely to be injured in a fire; 15,000 visits to emergency departments are caused by CO poisoning every year. Yet only about one-third of U.S. homes have CO detectors. Sources of the gas include faulty furnaces, clogged chimneys, and electrical generators. Signs of poisoning include headache, fatigue, nausea, and dizziness.

Find the best smoke detectors and CO alarms in our buying guide.

Install smoke detectors, $12 and up, and CO alarms, $30 and up, near bedrooms and on every floor of your house, including in the basement. Consumer Reports' tests found that smoke alarms that use ionization technology were great at detecting a fast, flaming fire, such as burning paper, but poor at detecting a smoldering fire, as in a couch or mattress. The opposite was true of photoelectric smoke alarms.

But some combine ionization and photoelectric technologies to cover both types of fire, such as the First Alert 3120B, $30, and Kidde PI2010, $30, which were tops in our new tests. If anyone in your house is hearing-impaired, consider installing a smoke alarm that uses a flashing light or vibration.

As for CO detectors, the First Alert CO615, $30, stand-alone monitor was excellent at detecting high levels of the gas.   

Here's what to consider before buying and installing smoke detectors and CO alarms:

• Mount smoke detectors on the ceiling or high on a wall. To avoid false alarms, don't mount ionization smoke alarms in the kitchen, where burnt toast might set them off, or near sources of steam such as bathrooms or the laundry room.
• Make sure your alarms are up to snuff.
  
• Don't install CO monitors in breezy areas, such as near a fan or an open window, where fresh air can cause a misleadingly low CO reading. Also avoid mounting the monitors in direct sunlight that can damage the units, in the kitchen or near any cooking appliance, in the garage, or near the furnace or water heater.
• The life expectancy of smoke detectors is generally 10 years, after which point their sensors can begin to lose sensitivity. The test button only confirms that the battery, electronics, and alert system are working; it doesn't mean that the smoke sensor is working. To test the sensor, use an aerosol can of smoke alarm test spray (about $10) that simulates smoke, which is available online and in some hardware stores.
  
• Replace CO alarms every five to seven years. Check the label on the bottom of detectors and replace any that are older than that.
• Make a fire escape plan for your household and practice it. 
• Keep a fire extinguisher accessible. 
  —Sue Byrne