The First Alert Ten-Year 2-in-1 photoelectric smoke detector with carbon monoxide alarm features our new slim design and maximum protection. It's protection at its finest and lasts a full 10 years without the hassle and expense of twice a year battery changes. The sleek new design is half the size of standard alarms and looks elegant on your wall or ceiling, blending in easily with decor. Our patented smoke entry system allows for a direct path to the smoke sensor, helping to minimize nuisance alarms that often come from cooking smoke or shower steam.