Pets have always been a major cause of false alarms in domestic intruder alarm systems. Although great strides have been made in detector technology, we have yet to see a totally foolproof pet “immune” detector that does not compromise the catch performance of the detector.

However, there are many very good pet “friendly” detectors on the market that are reasonably secure providing that they are correctly installed.

What we need to ask ourselves is “How big is a pet?”

In industry terms, we consider a pet as being around the size of a Jack Russel, Maltese Poodle, small Spaniel, cat, etc. for indoor use. Most detectors will see a larger animal as the size of a human if it gets close enough to the detector. In fact, at close range, a cat may be seen as the size of a tiger.

Most pet “friendly” detectors will not detect pets, provided the pet stays on the floor. But what about a cat climbing up the curtains or jumping on furniture? This becomes a real problem if the cat gets too close to the detector and will most likely cause false alarms.

While a cat on its own may not produce much infrared, a number of cats or dogs moving together in a bunch will also increase the total amount of infrared seen by the detector.

When designing a detector, the first priority is to detect a human target of a specified temperature, within a specified distance, at a specific speed with reference to the background temperature of the area.

The closer a human target is to the detector the easier it is to detect it as the infrared emitted by the target gets stronger.

Although a pet may not emit sufficient infrared while on the floor, the closer it gets to the detector, the easier a detector will detect it and may then see it as a larger target or a human.

The trick is to ensure that the detector is installed so that it is neither near the curtains nor looking directly at furniture or cupboards that may be accessible to your pets. It is preferable to face the detector in an area free of obstructions.