Nothing changes on its own. The system keeps running exactly as it was left.
Set by hand — At the end of the shift someone drops the speed from 100% to 50%, and in the morning someone puts it back.
2 steps a day — Roughly 500 a year, and not one of them is verified by anything.
Easy to miss — A late shift, a locked room, a colleague off sick, and the step simply doesn't happen.
Nothing looks wrong — An empty hall ventilated at full power until 07:00 leaves no trace anyone notices the next morning.
See what the system is actually doing, hour by hour.
3 levels, not guesses — Off, reduced, or full: the sensor reacts to set thresholds on the fan circuit.
The real week — When the power came down, when it went back up, and every night it never came down at all.
Alert when it's late — Past the time it should have dropped, the message reaches you immediately.
Mornings too — Confirm full power returned when the shift started, not an hour before it.
Nothing rewired — No changes to the control circuit, no integration with building automation.
Know whether the ventilation was turned down when it should have been — and keep the record that proves it.