 You may only have a single type of smoke detector. The original smoke detectors that came along in the mid-70s and to this day are called ionization. They rely on a tiny radioactive element and a detector. And if smoke gets between those two, the alarm goes off. That's fine. But there's another kind of... But that's good for quick flaring fires. There's another kind, smoldering fires, which turns out to be the more...