The 3-pack of First Alert CO600 Plug-In Carbon Monoxide Detector helps protect your family in multiple rooms. The alarms feature an 85-decibel alarm and an electrochemical sensor and easily plug into any standard outlet with no additional mounting necessary. One button silences any nuisance alarms and also tests detector functions. And an end-of-life signal enhances your safety by letting you know when it s time to replace the unit. Keep your family safer by installing units on multiple levels and in each bedroom.