Today the window of escape time in flaming fires is 3 minutes compared to 17 minutes in 1976, because fires today burn hotter and faster therefore leaving people less time to safely escape than 40 years ago. Smoke alarms and fire alarm systems provide value when building occupants are awake, but their greatest benefit is when the occupants are asleep. Most commercially available audible alarm notification appliances produce an audible fire alarm signal between 2KHz and 4KHz, and nearly all integral smoke alarm sounders produce a 3KHz audible alarm signal. Numerous research studies have concluded that a low frequency audible alarm signal with a fundamental frequency of 520 Hz is the most effective signal for awakening people who are hard of hearing, school age children and the elderly. This informative presentation will review the research studies and cover the low frequency signaling requirements in the 2010 edition of NFPA 72, National Fire Alarm and Signaling Code ®, UL 464, Standard for Safety Audible Signal Appliances, and UL 217, Single and Multiple Station Smoke Alarms.