Wow.
I am a nerd for Fire Safety in the house. Pops used to do the spur of the moment fire drills with the stop watch bit. Got worse about it when an ancient light switch started an electrical fire in the walls.
In most jurisdictions a simple visit to your local firehouse will yield free basic smoke detectors. At least one should be placed just outside any sleeping rooms, one in any corridors. Look at the potential smoke progression paths as they might lead toward a bedroom and set a detector there.
Also, some studies have shown that a smoke detector placed on the header wall of a door is not ideal in that in some instances the collection of smoke may take some time to develope in areas like that. Ideally, one would read the installation instructions closely.
Additionally, it is worthwhile to keep fire extinguishers in the house. I keep several 5 & 10 lb ABC type fire extinguishers. 1 in the Kitchen, 1 near the fire place, 1 in the garage, 1 near the brew rig.. And a couple spares. Some Insurance carriers will even offer a $50 savings per extinguisher on your premiums.
Cheers and be safe.