Picture a fire starting in a garage or downstairs rumpus room at two in the morning. A standalone alarm in that room goes off, but the bedrooms are upstairs, the doors are closed and the air conditioner is running. By the time anyone hears it, the smoke has had a long head start. Interconnected alarms are designed to close that gap.

What interconnection means

Interconnected smoke alarms talk to each other. When one detects smoke, every alarm in the system sounds at the same time. You hear the warning in your bedroom even if the fire starts at the far end of the house. That is the whole idea, and it is a simple one that makes a real difference to how much time you have to get out.

Wired and wireless interconnection

There are two ways alarms can be linked.

Hard wired interconnection

Mains-powered alarms are connected by an extra conductor in the cable running between them. When one alarm triggers, it sends a signal along that wire to the others. These systems run on 240 volts with a backup battery inside each alarm, so they keep working during a power outage. Installing them involves cabling in the ceiling space, which is electrical work for a licensed electrician.

Wireless interconnection

Many current hard wired alarms can also link by radio signal. Each alarm still gets its power from the mains, but the signal between them travels wirelessly. This is handy when getting a cable from one end of the house to the other would mean cutting into finished ceilings, or when you are adding an alarm to a granny flat or garage. There are also sealed lithium battery alarms that interconnect wirelessly, which suit some situations where mains power is not practical.

When interconnected alarms are required

New homes and some major renovations in NSW generally need hard wired, interconnected smoke alarms as part of the building approval. Your certifier will confirm what your plans need. For existing homes, the general rule is working alarms on every level, and interconnection is not always mandatory. It is, however, widely recommended by fire services, and it is the setup we suggest for most families.

Homes that benefit most

Some layouts make interconnection especially worthwhile:

Two-storey homes, which are common in newer estates around Shell Cove, Calderwood and Flinders.
Split-level houses on the escarpment slopes in suburbs like Figtree and Mount Warrigal.
Homes with a granny flat, studio or converted garage where someone sleeps away from the main house.
Long single-level homes where bedrooms sit at one end and the kitchen and laundry at the other.
Households with people who sleep heavily, older relatives or anyone with reduced hearing.

Mixing brands is a problem

Interconnected alarms generally need to come from the same manufacturer and range to talk to each other reliably. One of the most common issues we see is a house where alarms were replaced one at a time over the years, leaving a mix of brands that no longer link up. The test button on one alarm sets off only that alarm. When that happens, replacing the whole set at once is usually the cleanest fix.

Testing an interconnected system

Press the test button on any alarm and every alarm in the house should sound. Walk around and check. Then try it from a different alarm. If one stays silent, it may have failed, lost its link or be an incompatible model. Hush buttons on most current models let you silence nuisance alarms from cooking without disabling anything.

Getting it done

Kalani installs interconnected smoke alarms in existing homes, extensions and new builds across the Illawarra. If you are planning a renovation, adding them at the same time as other renovation electrical work keeps disruption down. He will recommend wired or wireless linking based on your ceiling access, not on what is easiest for him.

To talk through your home, call or text 0424 400 346. Send a few photos of your existing alarms and a rough layout of the house, and Kalani can tell you what makes sense.

Interconnected smoke alarms explained