Kidde 2100637 ACDC Direct Wire Combination Smoke and Carbon Monoxide Alarm The Kidde 21006377 combination carbon monoxide and smoke alarm provides two important safety devices in a single unit. This alarm includes a voice warning system that announces "fire, carbon monoxide, low battery or smart hush activation". The voice alarm eliminates any confusion and clearly warns you and your family of a smoke or carbon monoxide danger, if your battery needs replacement or hush feature activated or cancelled.