How Many Sensors Does Your Home Alarm Really Need?

By Access Alarms Technical Team Updated

Most homeowners assume a proper alarm system means sensors on every door and window in the house. That is not the case. For most homes, five sensors or fewer is enough to give you solid protection.

Here is why, and how to think about placement properly.

Think Entry Routes, Not Every Opening

Burglars do not pick the most obscure way into a house. They go for the fastest, easiest entry point. That is usually a front door, back door, sliding glass door, or a window near the ground floor.

Good sensor placement means covering the routes someone would take to reach your valuables quickly. You do not need a sensor on the window in the second bathroom. You do need one on the door to the garage.

The Three Sensor Types You Need to Know

PIR Motion Detectors

PIR stands for passive infrared. These sensors detect movement in a room by picking up changes in heat. One well-placed PIR in a hallway covers far more ground than a door sensor on every room. If someone gets inside, the PIR catches them moving through the house.

Reed Switch Sensors

These go on doors and windows. Two small magnets sit side by side when the door or window is closed. When it opens, the magnets separate and the alarm triggers. Simple, reliable, and cheap to add.

Glass Break Detectors

Glass break sensors listen for the specific sound frequency of breaking glass. One detector covers a room with multiple windows. If your home has a big open area with several windows facing the same direction, a single glass break detector handles all of them.

The Australian Standards Requirement You Might Not Know About

Under Australian Standards for alarm systems, the alarm panel itself must be protected by a sensor. This is not optional. If someone breaks in and destroys the panel before the signal can be sent, the alarm is useless. A tamper sensor or a PIR covering the panel location satisfies this requirement.

Any alarm company installing to Australian Standards will include this. If yours did not mention it, ask.

Open-Plan Homes Need Fewer Sensors

If your living, kitchen and dining areas flow into each other without walls, one or two PIR sensors cover the whole zone. Older homes with smaller, separate rooms need more sensors because one PIR cannot see around corners.

An open-plan home of 200 square metres might need four sensors total. A similarly sized older home with a hallway, separate lounge, separate dining room and closed kitchen might need seven or eight to cover the same level of ground.

A Typical Home Setup

For most single-storey Brisbane homes, a basic but effective setup looks like this:

  • Front entry door: reed switch sensor
  • Back door or sliding door: reed switch sensor
  • Main living area: PIR motion detector
  • Hallway to bedrooms: PIR motion detector
  • Alarm panel location: tamper or PIR coverage

That is five sensors. For most homes, that is enough. Adding more is fine, but more sensors does not always mean better protection if the placement strategy is not right first.

Get a Quote for Your Home

Every home is different. A proper quote includes a look at your layout, entry points, and what you want to protect. Access Alarms installs alarm systems across Brisbane and South East Queensland.

Learn more about alarm systems or call us on 1300 049 969 to talk through your home.

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