How can I pick a smoke detector that only detects smoke and not heat?
TL;DR Your older detector, statistically speaking, is likely ionization, so your newer detector, which is photoelectric (both because you said so and due to current market conditions as explained below) may do better because it is different or simply because it is newer. But either way, the problem is likely steam and not heat because standard $ 10 - $ 50 residential smoke detectors do not detect heat.

Most residential smoke detectors do not detect heat. That is one advantage of sprinklers (aside from the fact that sprinklers actively protect people &amp; property, rather than just notifying you of a problem) - sprinklers have a fusible link that melts and lets the water through - no electronics involved. Sprinklers are required in many locations for new construction of all homes and/or for renovation of multi-family homes. But that is a separate topic. Back to smoke detectors. There are two basic types:

Ionization

Photoelectric


You can find a reasonably good explanation of the differences on Wikipedia.
But the short answer is that both types detect smoke, not heat, but they do it using different technology. Each one is better/faster at detecting different types of fires.
I just replaced one of my smoke detectors and the replacement is a photoelectric model. I found that unusual because for many years, ionization models have been the norm. In fact, my understanding is that the &quot;10 year smoke detector rule&quot; - instead of replaceable batteries, all residential battery powered smoke detectors now have a built-in maximum lifetime of 10 years - is based on two factors:

Practical - A lot of people take out the battery when the low battery chirps in the middle of the night and forget about replacing the battery until it is too late.

Technical - Ionization detectors are based on a teeny bit of radioactive material which, due to the laws of physics gradually becomes less effective. It doesn't matter whether there are any fires, ambient temperature &amp; humidity (which affect electronics in general), or whether the unit has ever been turned on.


I am not sure how much of the current debate over ionization detectors is based on &quot;Oh no, you want me to put a radioactive device in my house! The horror! We'll all become zombies/Godzilla! We're doomed!&quot; - to which I can say &quot;Let's ban bananas next!&quot; and refer you to the obligatory XKCD (thank you @spikey_richie), vs. an actual scientific analysis of which detectors work best overall when it comes to saving lives and property. But the end result is that several US states have banned or restricted ionization detectors (or alternatively, required photoelectric detectors) and major manufacturers and retailers far prefer to manufacture and sell a single product line across the entire country, so ionization detectors are rapidly disappearing from store shelves.