Standalone smoke alarms
The main function of a standalone smoke alarm is to alert persons at risk by way of
- Audible tones
- Usually around 3200 Hz due to component constraints (Audio advancements for persons with hearing impairments have been made)
- 85 DBA(decibles)at 10 feet
- Spoken voice alert
- Visual strobe lights
- 110 candela output
- tactile stimulation, e.g., bed or pillow shaker (No standards exist as of 2008 for tactile stimulation alarm devices.)
Some models have a hush or temporary silence feature that allows silencing without removing the battery. This is especially useful in locations where false alarms can be relatively common (i.e. due to "toast burning") or users could remove the battery permanently to avoid the annoyance of false alarms.
While current technology is very effective at detecting smoke and fire conditions, the deaf and hard of hearing community has raised concerns about the effectiveness of the alerting function in awakening sleeping individuals in certain high risk groups such as the elderly, those with hearing loss and those who are intoxicated. Between 2005 and 2007, research sponsored by the NFPA (National Fire Prevention Association link pls.. ) has focused on understanding the cause of a higher number of deaths seen in such high risk groups. Initial research into the effectiveness of the various alerting methods is sparse. Research findings suggest that a low frequency (520 Hz) square wave output is significantly more effective at awakening high risk individuals. Wireless Wi-Safe smoke and carbon monoxide detectors linked to alert mechanisms such as vibrating pillow pads, strobes and remote warning handsets have been found to support the groups above.
A Photoelectric smoke detector equipped with strobe light for the hearing impaired
Most residential smoke detectors run on 9-volt alkaline or carbon-zinc batteries. When these batteries run down, the smoke detector becomes inactive. Most smoke detectors will signal a low-battery condition. The alarm may chirp at intervals if the battery is low, though if there is more than one unit within earshot, it can be hard to locate. It is VERY common, however, for houses to have smoke detectors with dead batteries.