The access control was perfect – the door stood open for six hours
Access control knows who opened the door. It does not know whether the door was closed again. See how alarm sensors, alarm zones and auto-disarm catch forced entries, doors left open and jammed locks without false alarms.
A technician opens the door to a plant room at 08:12. Everything is exactly as it should be: valid key, right person, right time window. The log is impeccable.
Then he wedges a fire extinguisher in the door, because he needs to carry things in and out.
At 14:30 he drives home. The fire extinguisher is still there.
The access control did everything right and noticed nothing. It knows who opened the door. It does not know whether anyone closed it.
Four things a lock cannot see
Door left open
The lock was opened legitimately. The door simply never got closed again.
Forced open
The door was opened without a matching unlock. Somebody got in by a route other than the key.
Lock jammed
The lock tried to move and could not. The door may not be locked at all right now.
Low battery
The device is running down. Not yet a problem – but it is going to be.
All four happen after or around the access decision the system made. Which is why they have to be measured at the door itself.
Alarm zones: the sensor and the lock need to know about each other
The classic reason door sensors end up switched off is false alarms. The sensor shouts every time an employee with valid access walks through. After two weeks it is permanently disarmed, and then it protects nothing.
The answer is to tie the sensor to the locks in the same physical area. That grouping is an alarm zone.
Each alarm sensor is attached to an alarm zone, and the locks belonging to that zone can trigger auto-disarm:
Sensor state: ARMED
│
├─ Legitimate unlock of a lock in the alarm zone
│ └──► Sensor disarms automatically
│ (no alarm – this was the point)
│
└─ Door opens WITHOUT an unlock in the zone
└──► Incident: Forced open · severity: CRITICAL
With auto-disarm enabled, the sensor disarms automatically when any lock in the connected alarm zone is unlocked. The employee notices nothing. The alarm only fires when someone enters in a way that does not correspond to an access.
That single setting decides whether your sensors are still running in six months.
Armed and disarmed
A sensor can be armed and disarmed manually — for instance when an area is under construction and would otherwise alarm all day.
The system records when the sensor was armed and when it was disarmed. It sounds like a detail, but it is the log that answers the question when something goes wrong: was the monitoring even switched on that evening?
A sensor left disarmed that nobody remembered to re-arm is the most common reason an incident never gets recorded at all.
Forced open without a matching access is the critical signal
Of the four incident types, forced open is the one that changes something immediately.
The others are warnings: a door left open is usually carelessness, a jammed lock is usually wear, a low battery is a job for Friday.
A forced open without a matching key access is different. It means the door was opened and the system cannot account for how. That incident is recorded as critical and calls for investigation straight away.
It is also the type that becomes a candidate for a regulatory case if the site falls under NIS2 or CER. And because the incident carries a timestamp from the moment the sensor saw it, there is a documented moment of detection from which to count the 24-hour deadline.
Set against purpose sessions, the picture sharpens further: if there was an active session at the location, a forced open is probably a technician who used the wrong door. If there was none, it is something else.
Low battery is prevention, not a fault
It is tempting to treat battery warnings as noise. They are the opposite.
The CER regime requires preventive measures — measures that stop incidents arising. A lock that runs out of power at an unstaffed pumping station is a disruption that was signalled weeks in advance. At sites with neither mains power nor a network the sensors run wirelessly on batteries — including on top of an existing iLOQ system.
Because battery warnings are recorded as incidents like everything else, they land in the same history. When supervision asks how you work preventively, the answer is a list of warnings and when they were handled — not an assertion.
How to set it up
- Define alarm zones by physical area – not by the org chart. A zone is a place, not a department.
- Attach each sensor to its zone, and check that the locks people actually use to enter the area belong to that zone.
- Enable auto-disarm wherever there is normal traffic. This is the single most important setting.
- Leave auto-disarm off in areas where no access is normal – remote sites, emergency exits, sealed rooms.
- Review disarmed sensors monthly. A sensor that has been disarmed for four weeks is a blind spot, not a setting.
FAQ
What is an alarm zone?
A physical area that a sensor monitors and that one or more locks belong to. That association is what allows a legitimate unlock to disarm the sensor automatically instead of raising an alarm.
How do we avoid false alarms?
By enabling auto-disarm. When a lock in the connected alarm zone is unlocked, the sensor disarms automatically and normal traffic raises no alarm.
What is the difference between "forced open" and "door left open"?
Forced open means the door was opened without a matching unlock – someone got in around the access control. Door left open means the opening was legitimate, but the door was not closed again within what is permitted.
Can we tell whether a sensor was armed when something happened?
Yes. The armed and disarmed timestamps are stored, so it can be established whether monitoring was active at the relevant time.
Does a forced entry have to be reported to the authority?
It depends on whether it amounts to a significant incident under NIS2 or a significant disruption under CER. The assessment is yours – but the incident can be escalated into a regulatory case with the associated deadlines if the answer is yes.
Contact us
Want to catch the open door before it has stood open for six hours? Contact SnapKey.
Related articles
The CER Directive after 17 July 2026 – designated as a critical entity? The clock is running
The deadline for designating critical entities expired on 17 July 2026. If your organisation has been notified, you have 9 months for the risk assessment and 10 months to comply. Here is what CER requires of your physical security.
Energy Legislation and Access Control – Requirements for Critical Infrastructure
Understand energy legislation requirements for physical security and access control. Learn how SnapKey helps energy companies achieve compliance.
From incident to regulatory report in 24 hours – without guessing
NIS2 gives you 24 hours for an early warning. See how an access incident is recorded automatically, escalated into a regulatory case and filed on time – with countdowns, PDFs and an unbroken chain of evidence.