First Alert Onelink SCO501CN
Interconnecting CO detector/smoke detector
This CO and smoke detector combo has the ability to connect to up to 15 other Onelink home detectors -- that's helpful if you have a large home and worry that you may not hear an alarm sounding in a distant part of your home. Each unit is battery-powered, and they connect to each other by radio frequency. Experts say sensitivity is good with both CO and with smoke (this unit has a photoelectric fire sensor, which indicates the presence of a smoldering fire). One downside: This detector lacks a digital display, so you can't be sure of the exact level of carbon monoxide present. However, many owners feel its programmable voice alert, which loudly announces the location of the danger, easily makes up for this. The unit's manufacturer warranty is for five years, while its expected sensor life is six years.