Pet-Friendly Burglar Alarms: How to Stop Pets Triggering False Alarms
By the DC Fire & Security engineering team — installing and maintaining fire and security systems since 2010. Updated June 2026.
Quick answer
Pet-immune PIR sensors ignore heat signatures below a set size — typically up to 25kg moving at floor level — so most dogs and cats don't trigger them. The real-world fix is design, not just sensors: mount PIRs so pets can't get close at height (stairs, sofas, cat trees defeat naive immunity), use part-set patterns, and put contacts rather than motion sensors where animals roam.
How does a pet-immune PIR actually work?
A PIR sees moving heat across detection beams. Pet-immune models shape the beams and process the signal so a small body low to the ground doesn't accumulate enough 'score' to alarm, while a person-sized signature does. The 25kg figure assumes the pet stays at floor level — a 4kg cat on a bookshelf half a metre from the sensor looks bigger to the optics than a labrador by the door. That's why placement decides success more than the spec sheet.
Design rules that actually work with pets
- Mount PIRs where pets can't get near them at height: away from stairs, shelving, window sills and furniture they climb
- Prefer door/window contacts in pet zones: a contact doesn't care what's moving inside the room
- Use part-set: full perimeter armed, interior PIRs in pet areas omitted — intruders still hit contacts and non-pet zones
- Aim PIRs across rooms rather than at radiators, sunny patches or the hamster corner
- For strong cases (multiple large dogs, free-roaming cats at night): dual-tech sensors (PIR + microwave) cut false alarms further
What about cats specifically?
Cats are the hard case: they're small enough for immunity until they're suddenly 30cm from the lens on top of a wardrobe. Honest answer from installers: don't rely on pet-immune PIRs in rooms a cat owns overnight. Protect those rooms with contacts on the openings and put motion detection in spaces the cat doesn't access, or accept a part-set pattern that omits the cat's territory while keeping the shell of the building fully armed.
Frequently Asked Questions
Will a 30kg dog trigger a pet-immune PIR?
Do pet-immune sensors detect burglars as well as normal PIRs?
Can smart cameras with person detection replace PIRs in pet homes?
My current alarm false-alarms because of the dog — replace or fix?
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