Universal Security 4-in-1 Smart Alarm uses a single sensor to detect both CO and Natural Gas and protects against both fast flaming and slow smoldering fires. Microprocessor Intelligence provides superior nuisance alarm resistance, along with temperature and humidity compensation, self-diagnostics and Quick find alarm origination features. Perfect for new or replacement installations. This 120-Volt AC/DC hardwired alarm offers time-saving installation features, value and quality.