Carbon monoxide is nothing to mess around with, and the 9CO5 (KN-COB-B) carbon monoxide detector three-pack from Kidde is an effective way to monitor the potentially deadly gas. The battery-powered alarms (which take three AA batteries each, included) use electrochemical sensors to continuously gauge CO levels, then sound several 85-decibel beeps if they detect a dangerous amount. Electrochemical sensors are the preferred technology in CO detectors today, and are less susceptible to mistaken readings due to temperature or humidity changes.

These units come with a test/reset button, a green light that flashes every 30 seconds to let you know the alarm is working properly, and a battery lockout system, which makes it tough to close the cover without batteries installed. They also have an end-of-life alert that reminds you to replace the unit after seven years.

The 9CO5 (KN-COB-B) carbon monoxide detector three-pack from Kidde is covered by a 5-year limited warranty.


Pros: Battery lockout system
Cons: Fairly basic unit

Warranty
5 years, limited