It would have been nice to put up a photo of the actual swarm, but it was all a bit frantic trying to catch it before it absconded to under the neighbour's  facia board or into the inside of a post box. But the data is equally of interest:

The underlying theory of the whole thing is that measuring CO2 levels in the catch hive can help indicate and ultimately predict swarming. There's a whole load of other factors which are recorded, but CO2 was thought to be the most important. One of the great things about XGBoost is that it can automatically tell us which factor is ACTUALLY most important with a nice graphical display, but this will all come later when we have a bit more data to work with. One swarm aint enough.

Fortunately, I set the system up to calculate the max CO2 value in the last 48 hours as I knew that scouting bees would be active before the swarm actually materialized. What is really strange is that the scouting bees seem to have decided to spend the night in the catch hive, no doubt to check out the furnishings and raid the mini bar. After the swarm has now been collected and re-housed the CO2 patterns seem to have returned to normal.

Another indicator that I thought might be important is the gadget temperature since it already has a temperature sensor in it and is in full sunlight, just like a bee hive. It gets hot, but bees like this degree of heat and are more than capable of ventilating the hive when necessary.