Tamper proof design provides a higher level of security to prevent battery removal Combines the benefits of both Photoelectric & Ionization technology in one alarm Gives a decade of peace of mind Maintenance Free Battery Back-up Power - No batteries to replace for the life of the alarm Eliminates annoying low battery chirps 10 year sealed batteries provide continuous protection - even in the event of a power outage 2-in-1 alarm protects against both fast flaming and slow smoldering fires Smart Alarm Technology virtually eliminates nuisance alarms. Ideal for installation in EVERY room Deactivation key switches alarm off and makes batteries and alarm safe for disposal (once alarm reaches the 10 year product end of service life) Lock-out feature prevents deactivated alarm from being reinstalled Choose this alarm if you are looking for an alarm with superior nuisance alarm resistance 10 year product end-of-service life warning sounds when it is time to replace alarm This alarm is suitable for installation in houses, apartments, dormitory, hotels, & manufactured housing For maximum protection, install an alarm inside every bedroom, outside every sleeping area and on every level of the dwelling ECO Friendly - Reduces environmental waste & eliminates disposal of up to twenty 9 volt batteries Automatic temperature and humidity compensation continuously adjusts to variations in environmental conditions , reducing nuisance alarms For added security, ta