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Why Do Spiders & Insects Trigger False Alarms? (And How to Stop It)

12 September 2026 2 min read

Why Do Spiders & Insects Trigger False Alarms?

If your burglar alarm has ever gone off with no intruder in sight, a spider or insect could be the culprit. Small pests are one of the most common, and most overlooked, causes of false alarms in monitored properties.

How a Spider Can Set Off Your Alarm

Motion detectors, including passive infra-red (PIR) sensors and dual-technology microwave sensors, work by detecting movement and heat. A spider crawling across the front of a detector, or building a web directly in its path, can be enough to trigger it, especially in detectors without proper insect shielding.

This is more common in autumn, when spiders move indoors looking for warmth, and in properties left unoccupied for a few days.

Why False Alarms Are a Bigger Problem Than You Think

A single false alarm is usually just an inconvenience. But repeated false alarms can have serious consequences:

  • Engineer call-out and reset charges

  • Police forces downgrading or withdrawing response to your address after multiple false activations

  • Potential impact on your insurance cover if police response is withdrawn

This is why how your alarm is monitored matters just as much as the alarm itself.

How AMCO's LiveTalk Monitoring Prevents Unnecessary Call-Outs

With standard alarms, every activation can trigger a police call-out, spider or not. With AMCO's LiveTalk monitoring, our trained operators listen in to the property the moment an alarm activates. If there's no sign of an intruder, we can verify this immediately and stand down, no wasted call-outs, no unnecessary police involvement, and no needless stress.

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How to Reduce False Alarms from Pests

A few simple habits can cut down on pest-triggered alarms:

  • Regularly dust and clear cobwebs from around motion detectors

  • Check detector housings are properly sealed and undamaged

  • Use insect deterrent spray near (not directly on) the detector, most pests avoid it

  • Book an annual maintenance check to ensure your detectors have proper insect shielding fitted

Getting Unwanted Alarms? Talk to AMCO

If false alarms are becoming a regular problem, it may be time for a system check or an upgrade to LiveTalk monitoring, so every activation is verified before anyone is called out.

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