Fall detection in personal alarms: how it works and what it misses

What a fall detector senses

Inside the pendant is a motion sensor, the same family of part that tells your phone which way up it is. It watches for the shape of a hard fall: a sudden drop, an impact, and then stillness. When those three things arrive in the right order and the impact is strong enough, the sensor decides a fall has happened.

That shape is the whole trick, and it explains both what fall detection does well and what it cannot do. A trip on the back step, a faint at the letterbox and a collapse in the kitchen all look like a fall to the sensor. A slow slide down the shower wall, a slump sideways in an armchair and a fall broken by a hand on the bench do not, because there is no sharp impact to read.

The watch works the same way from the wrist. The wrist moves on its own all day, so the watch has to be a little more sure before it acts, and a fall onto the other arm can read differently from a fall onto the side the watch is on. The pendant, at chest height, reads the body rather than a limb. Both detect hard falls only.

What happens next

When the sensor reads a fall, SOS Everywhere raises the alarm as if the button had been held. The pendant rings the first contact on the list. We set it to ring each person for 15 seconds, then the next, and to go round the list up to five times before it stops. Anyone with texts switched on gets a message that starts with the name you gave the pendant. In the SOS Everywhere app, the alarm appears in the list by type, marked as a fall, and the pendant reports where it is every 10 seconds for 10 minutes.

Whoever answers can talk to the wearer through the pendant. That conversation is where most fall alarms end: the wearer says they are fine, or they say they are not, and the person who answered knows the address, the neighbour with the key and whether to call 000. If you add 24/7 monitoring, our monitoring provider takes the call when none of your contacts answer, and does the same job.

There is no countdown and no cancel button on the pendant. Some alarms give the wearer 30 seconds to say it was a false alarm. We chose not to, because a person who has hit their head or is winded may not manage it, and a false alarm costs a phone call that ends in ten seconds. If the wearer sets it off by sitting down heavily, the first contact hears that and hangs up.

The falls it can miss

Be clear-eyed about this, because the sellers who promise automatic protection are not. The Australian Institute of Health and Welfare's reporting on falls in older people is where the scale of the problem is set out, and most of those falls are not the dramatic kind. They are a knee that gives way, a stumble on a rug, a slide from the edge of the bed.

A detector reads the fall it was built to read. It can miss a fall that ends in a chair or against a wall, a fall onto a soft surface, a fall where the wearer catches themselves halfway down, and a faint that folds rather than drops. It can also read a fall that was not one: dropping the pendant on a tiled floor, flopping onto the couch, a rough car ride. Sensitivity is how you trade those two errors against each other.

No fall detector catches every fall. Write that sentence down before you buy any alarm, ours included, and plan around it. The plan is the button, worn where it can be found without looking, on a wearer who has practised holding it.

Sensitivity from 1 to 9

In the SOS Everywhere app, fall detection is switched on or off and set from 1, the least sensitive, to 9, the most. Nothing is set on the pendant itself, so the family can change it from another city.

Start near the middle. Leave it for a fortnight and count the alarms. If the pendant rang the list twice for sitting down and never for a fall, go down a step. If the wearer had a fall it did not read, go up a step. Someone who gardens on their knees, plays bowls or drops into chairs usually ends up lower than someone who walks and sits gently, because their ordinary day has more impacts in it. A person with a recent fracture or a history of faints usually ends up higher, and their contacts should expect the occasional call that ends with "I'm fine".

Tell the contacts what a fall alarm sounds like before you switch it on. A call from the pendant's number with the wearer's name in the text, and the map in the app, is what they will get. The app page shows the screens.

Pendant or watch for falls

If falls are the main worry, the pendant has the edge. It sits at chest height on the lanyard, reads the body's movement, and stays on in the shower where a good share of falls happen, because it is rated IP67. The belt clip and the arm band move it, and the sensor still works, but chest height on the lanyard is the position it reads best from.

The watch is the right answer for someone who has worn a watch all their life and will take a pendant off. It detects hard falls too, it raises the alarm itself, and it carries the same caveat. Between the two, choose the one the wearer will keep on. Our page on choosing a personal alarm walks through the habits that decide it, and the pendant and watch pages have the specifications.

Why the button is still the main way to call

Everything above comes back to one idea. Fall detection is a second chance for the moment when the wearer cannot press the button. It is not a replacement for a button they can. The button is held for two seconds, it has no screen to unlock, and the wearer decides when to use it: chest pain in the night, a fright at the front door, a fall the sensor did not read.

So set up the alarm as if there were no fall detector. Wear it every day. Put three people on the list who will answer, a neighbour third. Practise holding the button together on the day it arrives. Then switch fall detection on, set the sensitivity, and let it be the backstop it is.

After a fall: what the family sees and does

A fall alarm arrives as a call. Answer it, and talk. If the wearer answers back and is fine, that is the end of it. If they do not answer or cannot, open the SOS Everywhere app: the map shows the pendant's last position, the address and the battery, and you can ring the pendant from a phone on the list, because it answers on its own. Then decide whether to call 000, go yourself, or ring the neighbour. Afterwards, the alarm stays in the app's list by type and date, which is useful when a GP or an occupational therapist asks how often falls are happening. If the falls are becoming frequent, that history is worth taking to the Support at Home conversation about what else the plan can fund.