Smoke Alarms: Ionization or Photoelectric or both?
The topic of selecting the best smoke alarm can be confusing. No sensor is perfect for every conceivable set of circumstances. We have known for many years that smoke alarms based on ionization sensors react faster to flaming fires than do smoke alarms using photoelectric sensors. Conversely, photoelectric smoke alarms react faster to smoldering fires than ionization alarms. The difference is a result of the physics of fire a flaming fires produce and smoldering fires produce different kinds of smoke (when you study it in a laboratory).
Research has shown that flaming fires are responsible for the majority of home fire deaths. In light of the flammability of home furnishings, this should be a significant concern for many homeowners (see http://www.youtube.com/watch?v=mulnwTNhV6Q) for a dramatic video comparing fire growth in modern furniture to fire growth in older furniture from Underwriters Laboratories).
There is a lot of pseudo-science out there that purports to show one type of alarm is better than another. Many of the websites are connected with individuals or companies that have a product to sell; others are simply misinformed. Despite appearances, what they offer is not based on science. The physics involved can be complex and confusing, and every fire is different. Credible fire researchers and safety experts are in broad agreement that both types of smoke alarm provide valuable safety to consumers (see the white paper at http://www.usfa.fema.gov/downloads/pdf/white-paper-alarms.pdf).
To summarize, it cannot be stated definitively that one is better than the other in every fire situation that could arise in a residence. Because both ionization and photoelectric smoke alarms are better at detecting distinctly different, yet potentially fatal fires, and because no one can predict what type of fire might start in a home, the USFA recommends that every residence and place where people sleep be equipped with:
a¢ Both ionization AND photoelectric smoke alarms, OR
a¢ dual sensor smoke alarms, which contain both ionization and photoelectric smoke sensors
Scientific studies show clearly that both types of smoke alarm provide adequate time to escape a home fire, if they are installed and maintained properly. USFAas website offers additional guidance on the installation of home smoke alarms at: http://www.usfa.fema.gov/campaigns/smokealarms/alarms/index.shtm
With recent advancements in sensor and microprocessor technology, we are certain that improvements in smoke alarms can be made. In recognition of this, the US Fire Administration has teamed with the Consumer Product Safety Commission (CPSC) and Oak Ridge National Laboratory to conduct research to demonstrate a next generation home smoke alarm. The first report of progress on this project can be downloaded via our website at: http://www.usfa.fema.gov/media/press/2012releases/062012.shtm it is a technical report, but it shows clearly our commitment to improving this technology.
Others are involved in smoke alarm research. You may appreciate this piece from Underwriters Laboratories:http://www.ul.com/global/documents/offerings/perspectives/regulators/SmokeAlarmsInModernResidences.pdf
