Every home should have smoke alarms, and CO alarms are a must in all homes with fuel-burning appliances such as a furnace, water heater, range, cooktop or grill. Even an all-electric home may benefit from a couple of CO alarms, because using a generator during a blackout or a gas power washer after a flood produces CO. You need alarms that detect flaming and smoldering fires for each bedroom, with at least one set on each level, including the attic and basement. You should also have a CO alarm on each living level, in the basement, and near (not inside) an attached garage.
You can buy smoke and CO alarms at hardware and home-improvement stores and online. Smoke alarms are relatively inexpensive, starting at about $15 for basic models. CO alarms cost $35 and up. Check the package to make sure smoke alarms meet Underwriters Laboratories Standard 217 and CO alarms meet UL Standard 2034. Also look up the date of manufacture on the back of the alarms. These devices lose their sensitivity over time, so the fresher, the better. For performance data on specific models, see our Ratings of CO and smoke alarms, available to subscribers.
None do it all
Our tests of 25 alarms show that effective protection from fire and CO remains far too complicated. For example, 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. A few alarms combine ionization and photoelectric technologies to cover both types of fire, but they don't detect CO. And those that combine CO and smoke detection are effective for either type of fire, but not both. Our challenge to manufacturers: Produce a single device that senses both types of fire and CO.
Strength in numbers
Getting all of a home's alarms to communicate with one another poses another hurdle. Interconnected alarms all sound simultaneously when any one is triggered. Thus, they can warn you, say, of a fire or CO leak in the basement when you're asleep upstairs. You can use adapters to connect hard-wired alarms, even those made by different manufacturers. But wireless alarms can communicate only with other wireless alarms of the same make, since manufacturers use different frequencies. The industry needs to fix that problem as well.
Do your homework
Before you shop, check your town's or county's regulations. Details such as types of alarms and placement differ from one jurisdiction to another. Also contact your insurance company. Some insurers offer a 5 percent discount for homes with smoke alarms.
Proper installation and maintenance are critical
Follow the instructions in the owner's manuals. A few rules of thumb: Smoke rises, so mount smoke alarms on the ceiling or high on the 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 a bathroom, laundry room, or sauna. Don't install CO units in the kitchen or near any cooking appliance, in the garage, or near the furnace or water heater. And avoid breezy areas-around fans, vents, air conditioners, doors, and open windows, where fresh air can cause a misleadingly low CO reading. Keep CO alarms out of direct sunlight.
Test smoke and CO alarms weekly and vacuum them monthly. Follow the manufacturer's recommendations on battery replacement. Alarms have a limited useful life. Replace CO alarms every five years and smoke alarms every 10 years. In addition, prepare a plan of evacuation in case of a fire or CO emergency, and have everyone in the family practice it like a fire drill every few months.
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