The FireAngel WST-630-BNLT is a wireless, linkable smoke detector. Expand the smoke detector with any of FireAngel''s Wi-Safe 2 linkable products and fully secure your home. Link up to 50 smoke detectors together so you'll hear the alarm go off in every room. The 85-decibel audio signal will make sure of that. Test the smoke detector regularly using the test button, so you can be absolutely sure that it works. The detector runs on 2 lithium batteries and has an average life span of 10 years.