Well, I learned tonight that my neighbor’s smoke detector is audible through the wall.
Unfortunately, this is the neighbor who goes camping a lot, and so has a few 1lb cylinders of propane in his closet. The same closet that shares a wall with my closet, where I have my safe, ammo, primers, and powder (all safely stored in accordance with appropriate regulations and common sense). Not to mention the hazmat storage container hamper for dirty laundry. Whee.
Fortunately, the alarm was set off by his cooking, and not from his apartment being on fire. When I went outside to investigate, his wife was fanning the door to blow the smoke out. I helped them silence the alarm and offered my box fan to help clear out the smoke.
At least I know that the smoke detectors are audible through the walls, which should help if there’s ever an emergency.