SUPERIOR ALARM PERFORMANCE: Proven performance for sensitive detection of dangerous carbon monoxide (CO) leaks; a powerful 85 dB alarm tone will sound throughout your home and instantly alert those in danger ACCURATE CO READINGS: Accurately reads CO build-ups from 30 to 999 parts per million (PPM); a backlit digital LCD screen provides a clear display during both night and day FULLY-FEATURED: Malfunction warning, low battery warning, end-of-life indication, and silence mode enabled; surface mounted technology (SMT) and anti-RF technology (radio frequency will not interfere with the unit) ensure steady performance EASY INSTALLATION: All mounting hardware is included for fast and simple installation in minutes, including 2 screws, 2 anchor plugs, and a 9 V alkaline battery with 3-5 years of life QUALITY ASSURANCE: Comes with a 60-day money-back guarantee, 5-year warranty, and lifetime customer support with a response time of 24 hours ATTENTION: ONLY detects carbon monoxide (CO), NOT carbon dioxide (CO2)