The Google Nest Protect is a smart smoke and carbon monoxide alarm that thinks, speaks, and alerts your phone. This 2nd generation wired model (S3003LWES) features a Split-Spectrum Sensor that uses two wavelengths of light to detect both fast-burning and slow-smoldering fires, a critical advancement given that modern fires can engulf a room in less than 5 minutes compared to 30 minutes in the 1970s. The alarm includes a 10-year electrochemical carbon monoxide sensor, the most accurate type available, to detect this invisible, odorless poison.

The device communicates with a friendly human voice that provides early warnings and tells you exactly where the danger is located. When one Nest Protect speaks, they all speak throughout your home, so the alarm in your bedroom can alert you to smoke downstairs. You can hush false alarms from your phone using the Nest app instead of frantically waving a towel, and receive mobile alerts when something is wrong even when you are away from home.

Nest Protect performs over 400 self-checks daily on its batteries and sensors, and uses Sound Check to quietly test its speaker and horn monthly. The device features Steam Check technology with custom algorithms and a humidity sensor to distinguish steam from smoke, preventing shower-induced false alarms. Pathlight illuminates your way when you walk underneath it at night, with adjustable brightness levels. The Nightly Promise displays a quick green glow when you turn off the lights, confirming all systems are functioning properly and there will be no 2 AM low-battery chirps.

The wired model connects to AC 120V power with three long-life backup AA batteries (Energizer Ultimate Lithium L91) included. It measures 5.3 inches in diameter, 1.6 inches deep, and weighs 13.2 oz. The device includes Wi-Fi connectivity (802.11b/g/n at 2.4GHz), 802.15.4 wireless, and Bluetooth Low Energy for seamless integration with the Nest ecosystem. Additional sensors include temperature, humidity, occupancy (120° field of view up to 20 feet), ambient light, accelerometer, and microphone. Certified to UL 2034, UL 217, and NFPA-72 safety standards with a 10-year lifespan.