A bit of information you may or may not be aware of, but it would seem that interlinking different brands of smoke alarm may not work correctly. I'm planning to add in some interlinked mains-supplied battery backed-up smoke/heat/CO detectors. So, I went to the Kidde website to look at a few and found the following in the FAQ: Which seems a bit stupid, but that's the situation. So, if you are adding to an existing system or replacing the odd failed unit, you should probably aim to replace like with like. Does anyone here have any experience of Kidde's domestic products? Any good? I'm looking to put a CO alarm and heat alarm in the kitchen (the only room in my house with gas appliances), optical alarms in the bedrooms and ionisation alarms in the hallways and living room. I am planning on having a fireplace in the living room reinstated at a later stage to burn wood and/or coal... would ionisation be the correct choice?