When the chirp starts at two in the morning and Dad is already reaching for a dining chair, here is how to tell a battery he can swap with you from a job that belongs to someone with a real ladder.

It always starts at night. One small chirp, then a long silence, then another chirp just as everyone is falling back asleep. Mom knew which alarm it was before she was out of bed. She probably kept the spare batteries in the drawer by the phone and knew which ones took which kind.

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Now it is Dad, and Dad has a plan. The plan is the dining room chair, the one with the slightly wobbly leg, carried into the upstairs hall. He has changed a thousand batteries. He does not need a crew. And he is probably right that he knows how. The question is not whether he knows how. The question is what this particular job asks of a body standing on a chair in the dark, and whether the alarms in this house are the simple kind or something more.

So before you decide whether the two of you do it together or someone gets hired, walk the house with him. It takes about twenty minutes and it settles the argument better than you can.

Follow the chirp before you decide

Go room by room and look up. You are counting and noticing, not fixing anything yet. For each alarm, check:

Where it is. Bedroom, hallway, kitchen, basement, top of the stairs. Write it down. Most families are surprised by the count.
How high it is. A flat eight-foot hallway ceiling is a different job from the ceiling above the stairwell or a vaulted living room. If he would need to stand on anything taller than a sturdy step stool, note it.
What kind it is. Twist it gently off its base if you can reach. Some run on a battery alone. Some are wired into the house and only keep a battery as a backup. Some have a sealed battery that is not meant to be replaced at all, so the whole alarm gets swapped when it gives out. Wired alarms usually have a wire connector on the back and a small light on the front.
The date on the back. Most alarms have a manufacture date and replacement guidance printed on the label. If the date looks like it came from the same decade as the wallpaper, that alarm may be asking to be replaced, not just fed.
Whether they talk to each other. Press the test button on one. If several go off together, they are linked, and replacing one may mean matching the others.
Whether any are carbon monoxide alarms too. Some combine both. The label will say.

You will come out of that walk with a list. That list is what you are actually deciding about, not the chirp.

Do it together when

This can be a good job for the two of you, and there is something to be said for letting him be the one who knows where the batteries go. Do it together when:

The alarms are on ordinary ceilings he can reach from a step stool with a handle to hold, not a chair.
They take a battery he can open, and he can work the little door or clip without fighting it.
The dates on the back are still inside the replacement window printed on the label.
You are physically there. Not on the phone, in the room, holding the stool.

A good way to split it: he names which alarm, you climb, he hands up the battery. Or the reverse, if he insists and the stool is a good one. Then he presses the test button and you both wince at the noise. If you make it a standing appointment, with the same day each season and the same drawer for the spares, it stops being a midnight crisis and becomes one more thing the house does.

Hire it out when

Some of the list is not a family job, and saying so is not a comment on Dad. Bring someone in when:

Any alarm is over a stairwell, a high ceiling, or anywhere that takes a real ladder. A fall off a ladder in an empty house is the whole reason you are reading this.
The alarms are wired into the house and need replacing, not just a fresh backup battery. That is electrical work.
Several alarms are past the date on their labels. Swapping the whole set at once is often easier with someone who does it for a living.
They are linked together and you are not sure which new ones will work with the old base.
The house is missing alarms where you expected one, like outside bedrooms or on a floor that has none.

Who to call depends on the job. A handyman can often handle battery alarms on high ceilings. Wired replacements are usually a job for an electrician. Some local fire departments run home smoke alarm programs, so it is worth calling the non-emergency line and simply asking. If you are in the St. Louis area, the Local Help page is a good place to start.

What to ask whoever you hire

Before anyone climbs anything, ask:

Will you test every alarm in the house, or only the ones I point to?
Will you check the dates on all of them and tell me which ones are due?
If they are wired or linked, will the new ones work with what is already there?
Will you show Dad and me how to test them and silence a false alarm?
Will you take the old alarms and batteries with you?
Can you leave a written list of every alarm, its location and its type?

That written list is worth more than the visit itself. Tape it inside the cabinet where the spares live.

Then find out whether he can hear it

This is the part nobody thinks to check. An alarm that works perfectly is only useful if it wakes him. One evening, with his permission, have him go to bed, or at least lie down with the bedroom door shut the way he sleeps, maybe with the fan or the radio on if that is his habit. Press the test button on the alarm nearest the bedroom, then the one farthest away. Ask him what he heard, and from where.

If he heard it clearly, good. If he said "Was that the microwave?" you have learned something important, and it is not something to fix with a new battery. Alarms made for people who do not hear well exist, with louder tones, lights or bed shakers, and whoever you hire can talk through options.

What to do tonight

If the chirp is going now, find which one it is and take that one down only if you can reach it from a stool with a handle. Otherwise leave it until morning and make sure the other alarms are working.
Put the dining chair back in the dining room. Say you need it for something. You do.
Find the spare batteries, check what kind they are, and put them in one place.
Start the list: every alarm, where it is, how high, what kind.
Tell him you would like to do the walk-through together tomorrow, in daylight. Daylight is a much better argument than you are.

When to ask the doctor

Bring it up at his next visit, or call sooner, if during any of this you noticed:

He seemed unsteady on the stool, or dizzy looking up.
He did not hear the alarm from his bed, or heard it but could not tell where it came from.
He could not remember which alarms were where, in a house he has lived in for years.
Small tasks with his hands, like opening the battery door, have become a struggle.

You are not asking the doctor about smoke alarms. You are describing what you saw, so the doctor has the whole picture.

For the good-week card

Add one line: Every alarm in the house has been tested this season, and Dad heard the one nearest his bed.

If you are just finding this site, Start Here walks through the first hundred days, one chapter at a time.

Dad Says He Can Change the Smoke Alarm Battery. Do It Together or Hire It Out? Count the Alarms and the Ladder Before You Decide.