The world’s first patented fire and smoke detector was a low-tech, dairy-based – no, that is not a misprint – design. George Andrew Darby, an English electrical engineer working in 1902, situated a block of butter between two metal plates. When the butter melted, the plates touched, connected a circuit and rang a warning bell. American Duane Pearsall, however, brought smoke detectors home – with far less mess – in the late 1960s. He designed an affordable, non-dairy “SmokeGard 700” model that boasted replaceable batteries. A revolution in home fire safety swiftly ensued.
“Today’s most effective smoke detectors combine two technologies – ionization and photoelectric – to alert people to a fire,” says Bob Hillier, Owner, Paul Davis Restoration of Greater Houston, Texas. “But the biggest considerations by far are installing and maintaining whatever models you choose. They must be present and in working order to save your life.”
Smoke alarms based on ionization technology place a tiny smidge of radioactive material between two electrically charged plates. This material ionizes the air space between the plates and allows a weak current to flow continuously. When smoke infiltrates the plate area, the smoke particles disrupt the ion flow, alter the current and trigger the alarm. Ionization alarms excel at detecting flaming fires.
Photo-electric models, on the other hand, excel at spotting slow, smoldering fires. These detectors shine an angled light across a chamber toward – but not directly at – a sensor. When smoke wafts into the chamber, the smoke particles reflect light into the sensor, activating the familiar piercing alert. “These technologies work slightly differently, which is why models that harness both technologies are preferable,” Hillier says. “Most current models for home do employ both, but it’s prudent to check the label to make sure before purchase.”
Once smoke detectors are installed in your home – situate at least one per level and one per sleeping area – be scrupulous about maintenance. Regrettably, more than a third of smoke alarms are inoperable because their batteries are either dead or absent. If yours are battery operated, replace all batteries yearly; many families choose New Year’s Day for this critical safety task. More and more detectors today are hard-wired into the home electrical system, ensuring continuous power and triggering all when one sounds. Virtually all hard-wired types contain battery backup.
“About 60 percent of fire deaths occur in homes that either did not have smoke detectors, or the ones that were present weren’t operational,” Hillier concludes. “Keep your family safe by paying attention to your smoke alarms!”
