Why does my burglar alarm keep going off? Causes and fixes for false alarms
A burglar alarm that seems to go off by itself usually has a cause you can trace: someone arming or disarming in the wrong order, a door left on the latch, or a motion detector that can see a heater or the dog. Check the app's event log to see which device triggered, fix that cause, then add settings and devices that catch mistakes early. Here is how, and what UK police do about repeated false calls.
Why does a burglar alarm go off for no reason?
There is usually a cause you can trace. It just isn't a burglar.
| Cause | Typical example | Fix |
|---|---|---|
| People | Forgot to disarm, wrong code, too slow to leave, someone still upstairs | One entry route, suitable delays, quicker keypads |
| Detector position | A motion detector that can see a heater, a fire or a sunny window | Move or re-angle it, or use a dual-sensor detector |
| Doors and windows | A contact magnet out of line, a window left open at arming | Re-align the magnet, check before arming |
| Pets | A cat on top of a cupboard | Pet-immune detectors, climbing spots out of view |
| Outdoors | Wet weather, sudden warmth or cold, wildlife or traffic in view | Correct aim, hoods and brackets, sensitivity set for the site |
| Panic buttons | A key fob pressed in a pocket | A panic button that needs a long or double press |
How do you stop arming and disarming mistakes?
Ajax, citing partner feedback, says most user-caused false alarms happen on entry or exit. Its hubs offer settings for exactly that:
- Entry and exit delays on the entry route only, so every other detector still alarms at once.
- Two-stage arming: the system finishes arming only after a second step, such as the final door closing.
- Unvacated premises: when nobody opens the exit door before the exit delay ends, the hub sets Night mode, not full arming.
- System integrity check: before arming, it looks for an open window, an open enclosure or a lost device, and can block arming or ask the user to confirm. Ajax ships it switched off.
The Ajax KeyPad TouchScreen wakes as you approach and accepts a code, a Tag fob, a Pass card or a phone over Bluetooth. Ajax says it needs external power to keep the screen always on. The KeyPad Plus touch keypad reads the same cards and fobs. The SpaceControl key fob can be set to respond only to a long or double press, which guards against pocket presses.
Where should detectors go so they only see intruders?
- Height. Ajax recommends 2.4 m for its MotionProtect and MotionCam indoor detectors.
- Heat. A passive infrared (PIR) detector reacts to moving heat, so keep heaters, fires and sunny glass out of view.
- Pets. Ajax rates those detectors for pets up to 20 kg and 50 cm tall when fitted as instructed. A cat on a bookcase sits higher, so keep climbing spots out of view.
- Awkward rooms. The MotionProtect Plus dual-sensor detector uses a K-band microwave sensor only to confirm what the PIR sees, which Ajax says cuts false alarms from heat sources such as fires and air conditioning.
- Doors. The DoorProtect door contact ignores vibration lasting up to 0.15 seconds. Fit its magnet to the moving part, on the side the detector's arrow shows.
- Outdoors. Fit the hood or bracket each detector was designed for, from our Ajax accessories and brackets.
What is alarm confirmation, and does it help?
It makes one trigger prove itself. Your installer picks a list of devices, and the hub raises a separate "confirmed" alarm only when two to five triggers from that list happen within 1 minute to 1 hour (by default, two within 30 minutes). Ajax says the Hub 2 (2G) wireless alarm panel supports up to nine of these confirmation zones.
It also matters for police response. NSI states that systems installed since June 2019 for monitored police response must meet PD 6662:2017 and BS 8243, the British Standard for confirmed alarms. Ajax lists Hub 2 as Grade 2 and publishes a PD 6662:2017 set-up guide.
Can a photo or voice check prove it was nothing?
Often, yes. The Ajax MotionCam photo-verifying detector takes one to five pictures when it triggers while armed, with infrared for the dark, delivered in up to 9 seconds at the default resolution. It works like the PIRCAMs in our Hikvision AX PRO buying guide.
The Ajax SpeakerPhone voice module is built for audio verification. For video, our Ajax cameras and NVRs can be set to record when an Ajax detector triggers, with the clip sent to the app.
The ICO says data protection law applies if your system captures images or audio from beyond your property boundary, so think about where cameras point and who could be heard.
What happens if the police get too many false alarms?
The police definition is wide: under the National Police Chiefs' Council (NPCC) requirements, an intruder alarm activation with no apparent damage or entry counts as false unless proved otherwise.
Police response applies only to monitored systems with a police unique reference number (URN), installed, maintained and monitored by police-recognised companies. Without a URN, as with bells-only and app-alert alarms, there is no guaranteed response: someone at the scene must call 999 or 101.
In England and Wales, the current NPCC requirements (2026 edition, updated June 2026) say:
- Two false calls in a rolling 12 months bring a warning letter.
- Three bring Level 3: keyholder response only, from at least 14 days after the withdrawal letter.
- To restore response, an unconfirmed system must be upgraded to BS 8243. A confirmed one needs the cause fixed and 90 days free of false calls, unless extra confirmation is added.
Police Scotland has its own policy. NSI summarises it as three false calls in 12 months dropping a system to Level Two, and two more to Level Three. Your installer can confirm which rules apply to you.
Ajax devices that help, with our prices
| Device | How it helps | Price inc VAT |
|---|---|---|
| Hub 2 (2G) | Confirmation, photo verification, arming checks | £161.53 |
| KeyPad TouchScreen | Wakes on approach, contactless and phone access | £235.38 |
| KeyPad Plus | Contactless cards and fobs | £116.54 |
| SpaceControl | Arming at the door, press protection | £47.31 |
| MotionProtect Plus | PIR with microwave confirmation | £63.00 |
| MotionCam | Photos on alarm | £124.61 |
| DoorProtect | Ignores short vibration | £50.76 |
| SpeakerPhone | Audio verification | £113.09 |
Prices include VAT, delivery is extra, and prices can change. See the full Ajax wireless alarm range or all our intruder alarms.
Our take
Nearly every cause above comes down to set-up and habits rather than a faulty product, so fix the entry route and detector positions before buying anything. Then add confirmation and a photo check, which turn "something moved" into evidence. For police response, the installer and monitoring company matter as much as the hardware. Zenith Security Co. has supplied security equipment since 2012; we supply Ajax equipment rather than fit it, and we can recommend a qualified installer depending on the job and area.
Want help choosing? Call 01902 902251, contact us online or visit our Wolverhampton trade counter. We ship nationally to England, Scotland and Wales.
False alarms: quick questions
Why does my burglar alarm go off at night?
Ajax says a common slip is choosing full arming when you meant Night mode, leaving indoor detectors live. Check the event log for the device that triggered.
How many false alarms before the police stop responding?
In England and Wales, three in a rolling 12 months under the 2026 NPCC requirements, with a warning letter after two. Scotland differs.
How long can a burglar alarm ring?
NPCC guidance says an external sounder should cut out after 20 minutes. In England and Wales, section 77 of the Clean Neighbourhoods and Environment Act 2005 lets a council officer enter, without force, to silence one ringing for over 20 minutes, or on and off for over an hour, that is likely to annoy neighbours.
Do I need a monitored alarm for police response?
Yes. It needs a police URN and must be installed and monitored by police-recognised companies. Otherwise someone at the scene must call 999 or 101.
Source: Ajax Systems blog, 13 May 2025, with NPCC security systems policy (2026), NSI, legislation.gov.uk and the ICO. Device figures are Ajax's own.
