In Scotland they are compulsory now. I have had interlinked alarms for about 10 years, would never be without them now.
Having a heat alarm in the kitchen. You don't get nuisance triggering, but to get triggering, there needs to be a large source of heat. I'm sure the temperature at the sensor has to be 55C, i.e already a flaming fire. So you are trading convenience for more damage/risk should something terrible happen. I know fire services promote heat detectors in the kitchen, but I prefer to have a smoke detector for the earliest detection and have both types in a kitchen in case there is a smokeless flame. Belt and braces!!
In Scotland, it is the law to have a heat detector in the kitchen. They should have given the householder the option. I put a heat detector and a smoke detector in my kitchens and workshop. I now have optical smoke detectors. Previously, I had ionisation. I prefer the ionisation, it gives the earliest warning. Sure, they are susceptible to triggering when the toast burns, but I found that comforting, like a regular self test. You can also pause them. The ionisation would trigger if I ran a petrol engine in the workshop, or burnt wood when cutting. I just found that very reassuring. I have had the kitchen thick with smoke when doing a major steak cooking and the optical sensors didn't go off.
I replaced the old system, because the detectors were end of life, but I may put the old ionisation detectors back up.
I went for the mains powered alarms. I already had the wiring.
Smoke Alarm,
Heat alarm and
Base
