Smoke alarms are designed to emit a loud, locally audible or visible signal from a wall or ceiling-mounted unit when smoke or fire is detected by that unit. The signal is intended to be disruptive enough to alert people of the need to evacuate the facility or home due to imminent danger.
The first smoke alarm was invented in 1890 by Francis Robbins Upton. It was not until the 1960s that households could benefit from an inexpensive version, and by the 1980s the latest models were becoming standard equipment in newly constructed homes and apartments. Now, 93 percent of American homes have smoke alarms installed.
There are two primary types of smoke alarms:
Detectors are generally installed on ceilings or high on walls within inches of the ceiling, as both smoke and heat rise and will most effectively be detected by the alarm at the highest level of the room.
According to the Consumer Product Safety Commission, residential smoke alarms should be installed on each level of the home, inside bedrooms, and just outside sleeping areas. But, each local or state government mandates very specific residential smoke detector placement and the fire marshal or building inspectors are always the best source regarding alarm regulations in a specific geographic area. When properly installed and working, smoke alarms offer the potential of escape from a deadly fire and reduce the risk of death by almost 50 percent.
Besides general failure due to faulty manufacture or improper installation, there are other causes of smoke alarm malfunction. The biggest and most basic concern is that of battery replacement. Homeowners often remove batteries due to a false alarm or fail to annually check functionality of existing batteries. Because they consist of electronic components, smoke detectors themselves do not age well. It is estimated by the National Fire Protection Association that standard smoke alarms require replacement every 10 years.
Beyond the battery and component longevity issues, each of the two main types of smoke alarms respond differently to emergency situations. Ionization alarms have been proven to respond better to flaming fire, yet perform below photoelectric alarms in situations of smoldering, smoky fires.
According to the National Fire Protection Association, there are several major areas of vulnerability and defect in smoke alarms:
According to the International Study of Sublethal Effects of Fire Smoke on Survivability and Health, somewhere between 310,000 and 670,000 people are exposed to smoke within their home environment each year. From these exposures, a confirmed average of 3,300 deaths and 11,500 injuries result. It is estimated that at least half of those deaths were incidences of smoke inhalation that would have not been lethal if the person had been removed from continued exposure.
The National Fire Protection Association reports that the fire death rate for Americans across all ages averages 10.3 deaths per million. For those over the age of 65, the death rate is over twice the average at 25.3 people per million. For those over age 75 years, the death rate increase to 32.9 deaths per million, three times the national average. Preschool children are also highly vulnerable, at 19.9 deaths per million.
Some examples of general product failure of smoke alarms include:
Below are some examples of death, property damage, and injury legal actions arising from smoke alarm failures or the failure of home owners to ensure the detectors were present and operational: