Security Advice · Ajax Alarms
Will My Pets Set Off an Ajax Alarm?
The most common reason a home alarm ends up permanently disarmed is not a fault. It is a dog. Here is how the detectors handle animals, and what setup actually stops the false alarms.
The short answer
- No – properly set up, pets should not trigger the alarm.
- Ajax MotionProtect detectors can be configured to ignore animals up to 20kg.
- For larger dogs the answer is placement, not sensitivity – cover doors and windows rather than open floor space.
- Sensitivity is tuned on site, around your actual animals, as part of the install.
- Photo verification means that even if something does trigger, you see immediately that it was the cat.
Why this matters more than it sounds
An alarm that cries wolf gets turned off. Not deliberately – it happens gradually. The dog sets it off twice while you are at work, a neighbour rings you about the siren, and within a month you are arming only the perimeter, then not arming at all.
So pet immunity is not a comfort feature. It is the difference between a system that stays armed and an expensive box on the wall. It is worth getting right at install rather than discovering it afterwards.
How pet-immune detection actually works
A passive infrared detector does not see shapes; it sees changes in infrared energy across a pattern of zones. A pet-immune detector is designed so that a small, low, warm body moving across the floor does not produce the signature that a person walking upright does.
MotionProtect detectors can be set to ignore animals up to 20kg. That figure is a design characteristic, not a magic threshold – a 19kg dog that jumps onto the back of a sofa has put itself at the height and profile of a person, and no sensitivity setting distinguishes those.
Which is exactly why the setup matters more than the spec.
What we actually do on site
Ask about the animals before choosing positions
How many, how big, where they sleep, whether they have run of the house at night, and whether they climb. A cat that sleeps on the back of the couch changes detector placement more than a labrador that stays on the floor.
Mount and aim for people, not floors
Detectors are positioned and angled so their coverage sits where a person moving through the space will be, and away from the routes and surfaces the animals use. Aiming is most of the job.
Cover entry points rather than open rooms
For larger dogs this is the whole answer. Instead of blanketing a lounge with motion coverage, the system watches the doors and windows – the places an intruder has to come through and the dog has no reason to be. Door contacts and glass sensors do not care how much the dog weighs.
Tune sensitivity, then test it
Sensitivity is adjusted on the day, in the actual rooms. It is a lot easier to do that at install than to be called back in a fortnight.
The bit that makes pets a non-issue
Even a well-tuned system will occasionally register something. What changes the experience is knowing instantly what it was.
With Ajax MotionCam, an alarm arrives on your phone with photographs of the room. If it is the cat on the bookshelf, you can see it is the cat on the bookshelf, and you go back to what you were doing. Without photos you get “lounge sensor triggered” and a decision you cannot make.
This is the honest reason we recommend photo verification in pet households more than anywhere else.
It is not that the detectors are worse around animals. It is that the cost of an unverifiable alert is much higher when there is a plausible innocent explanation moving around the house all day.
What about cats?
Cats are usually easier by weight and harder by behaviour. They are well under any pet-immunity threshold, but they climb, and a cat at head height on a shelf or a wardrobe presents much more like a person than a dog on the floor ever will.
The fix is the same as for large dogs: position detectors so that the surfaces cats use are outside the coverage, and lean on door and window sensors for the parts of the house where that is not possible.
Common questions
Will my dog set off the alarm?
Not if it is set up properly. MotionProtect detectors can be configured to ignore animals up to 20kg, and for larger dogs we position detectors to cover doors and windows rather than open floor space.
What about dogs over 20kg?
Placement does the work rather than sensitivity. We cover entry points – doors, windows, glass – which an intruder has to pass and the dog has no reason to trigger. It is a very reliable approach and it is what we use on most large-dog households.
Do cats set off alarms?
By weight, no. By behaviour, sometimes – cats climb, and a cat at head height reads more like a person than a dog on the floor does. We place detectors around the surfaces cats actually use.
Can pet immunity be adjusted after installation?
Yes. Detector sensitivity can be changed, and detectors can be repositioned. If something is triggering that should not be, that is a call-out we would rather have than have you stop arming the system.
Can I leave pets home alone with the alarm armed?
Yes – that is the entire point of setting it up around them. If you are nervous about it, photo verification means the first alert tells you what happened rather than leaving you guessing.
Does having pets make the system more expensive?
Not inherently. It can change which detectors go where, and pet households are the ones where we most often suggest MotionCam, which does add cost per detector.
Got a dog and a house you want to actually arm?
We set the system up around your animals on the day, and test it before we leave. Free site visit, itemised quote.