Fall detection without a camera — how radar sensors work and where they fall short

For an older family member living alone, a fall in the bathroom or bedroom is a real worry. A camera is the obvious answer, but few people want one in those rooms. Radar-based fall detection is an alternative that does not record a picture of anyone. It is a useful tool, but it is not magic, and it helps to know what it does and does not do.

How a radar fall sensor works

These sensors send out low-power radio waves, usually in the 60 GHz millimetre-wave band, and measure how the waves bounce back. From that, the sensor works out where a person is, how fast they are moving and how high the body is. A fall looks like a sudden drop in height and speed, followed by little movement near the floor.

Because the sensor returns movement data rather than images, it never produces a video or a photo, and it does not need a microphone. That is why it suits bathrooms and bedrooms.

What it is good at

• Rooms where a camera is not appropriate. Bathrooms, toilets and bedrooms.
• Darkness and steam. Radar does not depend on light, so a dark room at night is not a problem.
• No picture to leak. There is no footage to be stored, shared or misused.

What to understand before relying on it

• It is not zero data. The sensor can still tell that someone is present and how they are moving. Treat that as personal information, and keep the data on your own system where you can.
• Coverage is limited. A single sensor covers a defined area at a given mounting height, so a larger room or a long corridor may need more than one. Mounting position matters a lot.
• False alarms and missed falls both happen. Sitting down quickly, bending to the floor, or a pet moving around can look like a fall to a simple algorithm. A real fall under a blanket or behind furniture can be missed. Vendors often quote accuracy figures, but these are usually their own tests, so ask how they were measured and in what kind of room.
• It is a safety aid, not a medical device. It does not replace regular check-ins, a personal alarm the person can press, or proper care.

Making an alert actually useful

An alert only helps if someone sees it and knows what to do.

1. Decide who receives the alert, and who is the backup if the first person does not respond.
2. Decide what happens next: a phone call, a neighbour, a visit.
3. Test it. Have someone simulate a fall safely, such as lying down in the room, and confirm the alert arrives.
4. Consider a second signal, such as a sensor that notices no movement for an unusually long time in a room.

Common questions

Does a radar fall sensor record video or sound?

No. It returns movement data rather than images, so it produces no video or photo and does not need a microphone.

Is a radar fall sensor a medical device?

Treat it as a safety aid, not a medical device. It does not replace regular check-ins, a personal alarm the person can press, or proper care.

Can one sensor cover a whole room?

Not always. A sensor covers a defined area at a given mounting height, so a larger room or a long corridor may need more than one.

Where it fits in a smart home

Radar presence and fall sensors work well alongside the rest of a local system: a bathroom light that comes on dimly at night, a notification to the family, a door sensor that shows when someone has left. Keeping the logic on a controller in your home means the alert does not depend on a cloud service being reachable.

Thinking about care for a parent or relative at home? Tell us about the rooms and who will receive the alerts and we will suggest a layout and what to test first.