A lot of newer smoke detectors work on a photo-electric principle rather than by ionisation. That means they don't contain anything radioactive, and also tend to be more effective because they're less prone to false alarms.

I believe those are « fire detectors » as they sense the flickering light of a fire.

Flame detectors work via video feeds typically and analyze a video for flame and smoke patterns. Those come in both stand alone detectors and systems that work off of existing security camera feeds. (see also UV based detection)

They were referring to a photoelectric smoke detector vs ionization types. Both are still available but photo is much more common now days. They look exactly the same exterior wise, but it works by having a tiny light box where smoke goes in and changes the light the sensor is seeing. They can still cause false alarms because they are sensitive to dust and particulate matter, but they operate on intelligent addressable systems now which can adjust their sensitivity to some degree over time.

No. Those might exist too, but photo-electric smoke detectors definitely detect smoke.

Interesting person - he was actually making a Neutron Source rather than a reactor: https://en.wikipedia.org/wiki/David_Hahn#Creation_of_the_neu...