It starts as one short chirp somewhere in the dark, about once a minute. You wake up, decide it is nothing, and go back to sleep. Two nights later it is still going, and now you are standing in your mom's hallway at six in the morning trying to figure out which alarm is doing it.
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Listen for the pattern, not just the noise
A single chirp at a steady interval is the usual sign of a low battery. A chirp that keeps going after you have changed the battery, or one that comes in a different rhythm, can point to a different problem. Write down what you hear and when, even if it is only a note on your phone. Whoever picks this up next will want to know whether it started after a power outage, after a battery change, or out of nowhere.
Find which alarm is talking
Most homes have more than one alarm, and some are linked so that one unit can set off the others. Walk the house once with the lights on. Stand in each room in turn, because a sound in a hallway can seem to come from somewhere else. Many alarms have a small light that blinks when they chirp, so look for that. Press the test button on each unit and note which one answers with the loud test tone and which one stays quiet. The quiet one that keeps chirping is your suspect.
Check the date printed on the back
Every alarm has a date printed on the back or side. That date is the manufacturer's guidance for when the whole unit should be replaced, not just the battery. If the date has passed, a fresh battery may quiet it for a while, but the alarm is still due for replacement. Before you need one, buy the replacement and check the packaging for the battery type, so you are not guessing at the store with a chirp going in your head.
Decide who owns the battery and the ladder
This is where the split week shows up. If the spare batteries live in your kitchen drawer and the alarm is in your mom's house, you are the only one who can fix it, and it will wait until your next afternoon. Keep a small stash of the right batteries in her house, in the same place every time, and write that location on the list you already keep for her. Then ask who on the row is in charge of checking the alarms each month.
The ladder needs its own question. If the alarm is high on a ceiling and nobody in the family can reach it safely, do not let anyone climb to fix it just because they are there. Check the helper agreement for what it covers before any hired person touches a ladder, and if the answer is no, plan for a family member or a service to do it. If you need a name for someone who can help with that, the Local Help in St. Louis page lists places to start.
Ask your mom what she hears
People hear a chirp differently. If she sleeps with a fan running, or takes out a hearing aid at night, the alarm may be going for hours before she notices. Ask her plainly, without making it a test: have you heard the beeping at night? She may say no, and that may be true, which is why you should not rely on her ears alone. Ask whoever spends the evening in the house to listen for it on their next visit.
Name the day you check it
Pick one day a month and put it on the row where everyone will see it. Pressing the test button takes less than a minute per alarm. Once the check is written down, a chirp stops being a surprise at 2am and becomes a line on a list someone is already keeping. That is most of what this job needs: a name, a day, and a drawer with the right batteries in it.