Blog · Access control
How many people are inside right now? Counting occupancy with QR scans
The industry counts occupancy with sensors on the doors. QR scans do the same job for a lot less money, but only if you accept one uncomfortable condition: people have to scan on the way out too.
"How many people are inside?" is the question the safety officer asks, the one written into the venue licence, and the one nobody can answer when it is actually asked.
There are two ways to answer it, and it is worth knowing which one you are in.
How the industry solves it: sensors
The expensive answer is a sensor over every door — 3D camera, time-of-flight or radar — that detects whether each body is entering or leaving and keeps a running count. The technology is mature and delivers 97–99% accuracy.
It has one enormous virtue: it counts people, not credentials. It does not matter who they are, whether they have a ticket, or whether they are the electrician. If they cross the door, they are counted. For a capacity licence, which talks about people inside the premises, that is exactly what is being asked for.
And it costs what you would expect: hardware per entrance, installation, calibration, maintenance. It pays off in a permanent venue — a museum, a sports centre, a shopping centre — where it amortises over years.
For a three-day event in a marquee, it does not.
The other way: count with what you already scan
If someone is already scanning QR codes at the door, the counter is free: entries minus exits. Nothing to install, because the scan is already happening for another reason.
In QRACCESS that depends on one event setting, the scan mode:
Entries only. Each QR is validated on the way in according to its validity — single use, a set number of scans, or unlimited per day. Good for access control, but it gives you no occupancy figure: you know how many have come in overall, not how many are still there.
Entries and exits. Both movements are recorded, and live occupancy comes from that. Those same records are also the basis for attendance certificates.
Continuous scanning. For high-throughput gates, chaining scans one after another.
Occupancy, then, is a subtraction: those who came in minus those who went out. Simple, exact, no hardware. With one condition.
The uncomfortable condition: people have to scan on the way out
That is the whole thing. A sensor needs no cooperation; a QR scan does. If people leave through an uncontrolled door, or all at once when it ends, or simply cannot be bothered to pull out a phone to go home, the counter stays high: it says two hundred people are inside when the place is empty.
And that error does not correct itself. It accumulates.
So before promising anyone a live occupancy figure, answer three questions about the venue, not about the software:
Do people leave through the same door they entered? If fire exits get used as ordinary exits, or there is a side door to the car park, the count breaks. With a single controlled door, it works.
Is there anyone at the exit? Counting exits costs staff exactly like counting entries. If the event puts two people on the entrance and none on the way out, entries-and-exits mode is a setting that will not reflect reality.
What happens at the end? When the concert finishes everyone leaves at once, and nobody scans. That is normal and it is not a fault: occupancy is useful during the event, not at closing time. If the number you need is "how many came", that is the entries, and those are all there.
If the three answers do not line up, QR counting is not your tool — and it is better to know that beforehand than to discover it with the safety officer standing in front of you.
What happens when someone exits without having entered
It is more common than it sounds: the person who got in before you opened the desk, the one who already left and scans again, the one who uses the wrong scanner.
If those exits counted as normal ones, occupancy would drop below reality and eventually go negative. So they are recorded separately, with their own marker — "exit without entry warning" — and not as an ordinary exit. There is a setting that decides whether the app asks the door staff before recording it or just logs it: asked or not, the marker is the same; the setting only decides whether the question gets put.
It is a small detail with a large consequence: the counter does not drift because of odd cases, and you are left with a record of how many there were — which is a fairly honest indicator of how well the circuit was set up.
The same applies to zones
Total occupancy is usually the number the licence demands, but the useful one during the event is different: how many people are in each place. The main hall packed while the workshop next door sits empty is an operational decision — move staff, open another door, make an announcement — and it can only be taken if someone is watching.
With QR scans that means putting control on the internal doors that matter, not on all of them. And here credential-counting beats the sensor at something: it does not only say how many, it says who. That answers questions a counter cannot — how many of the people in hall A hold a two-day pass, or whether the press allocation is being respected.
In short
Sensors if the venue is permanent, if the count has to include everyone who sets foot inside, or if you cannot control where people leave. It is the right answer and it costs what it costs.
QR scans if you are already validating at the door, if the entry and exit circuit is defined, and if counting credential-holders is enough for you. It is free, it is switched on with one setting, and it gives you the "who" that a sensor does not.
What does not work is switching on entries-and-exits mode and assuming the number on the screen is the real occupancy. That number is only as good as the exit circuit you built, and no software fixes that.
If you want to see it working, set it up with ten test attendees: create the event in entries-and-exits mode, go in and out with the same QR codes, and watch the counter move from the dashboard. Half an hour tells you whether your venue can produce that number or not.