This is supposed to be one of the best rated dual sensor smoke detectors on the market. I have 5 of them.
The image shown here is either an old version or just the wrong version. In actuality, these detectors are much better looking. they are actually very round or domed. They also are rather tall, hanging lower from the ceiling than some. I don't mind since they don't look bad and they're rated well. You should check First Alerts website if you want to see what these really look like and haven't seen them.
The other detector that is rated similar to this is a Kidde Nighthawk brand. But it's reported to have more false alarms so I went with this one. I like the looks of this First Alert better, but that's just my opinion.
The photoelectric sensor uses a beam of light that sets off the alarm when broken by smoke. hence the term "smoldering". The ionization sensor is for the detection of flaming fires.
I think you'd have less time to react if the flames are already shooting that's why I like the idea of having a photoelectric cell. If a small fire starts, some smoke would be given off and set off the alarm before it got really big giving you hopefully more of a warning and more time. At least that's what I believe.
If this is in the kitchen as is mine and if you cook without a range hood drawing the smoke this detector would go off. If you toast on the dark side without a range hood pulling some smoke the detector would go off. I don't think of those as false alarms I think it's a testement to the sensitivity of the photoelectric detector which I like.
The alarm is quite loud. In the event I toast or cook and inadvertently don't have my range hood on and the alarm goes off I just twist the detector out of its base and put it on the counter until I'm done venting the smoke. And that smoke by the way, is barely perceptible with the eye, which is a testament to the sensitivity of this smoke detector.
Installation is a piece of cake. Battery replacemnent is equally simple. Actually more simple. There's a little door you open and pop the battery into while the detector is installed. You don't have to pull it down. although, it's just a simple twist to remove.
Also, you can test the detector with any TV remote. You can shut it off with a remote as well but I just use the external button for both.
I'm very pleased with these, as I stated I have 5. I bought them all through Amazon at different times and had no trouble with shipping. They came fast, were packed well and I feel a bit more comfortable having them up.