Nest Labs - S3004PWBUS Nest Protect 2nd Generation Smoke and Carbon Monoxide Alarm Pro Battery - White. Speaks up to tell you whatfts wrong and where the problem is. Sends alerts to your phone in case you aren't home. Just burned the Toast? App Silence lets you quiet the alarm from your phone. Every second counts. The Split-Spectrum Sensor detects fast and slow burning fires. It can see the invisible poisonous carbon monoxide you can't. The long-lasting sensors help keep you safe and sounds for up to 10 years.