Your smoke alarm needs to use the signal in the current version of NFPA 72, the US National Fire Alarm and Signaling Code. So you will probably need a US smoke detector less than a handful of years old. The alarm should be in direct earshot of the camera so the sound is not distorted or attenuated. You would need to play the signal for a few cycles so the camera can identify it.
When it alerts you it should NOT be in the form of a simple sound alert , it should identify it as a smoke or CO alarm.
I have never actually used simple sound alerts because they trigger on ANY sound – house creaking, whatever. So simple sound alerts are turned off for me in Event Recording > Sound. To get Fire alarms, sound is on under Notifications, though (and also under Alarm Settings, obviously). I also have sound detection sensitivity is also set to 100 under Detection Settings.
I just tested with 4 or 5 cycles in my hallway and I got an “Smoke alarm sound detected” alert from 2 cameras along with a couple of corresponding 12-second clips labeled “Smoke alarm sound”.