I got FreeOTP from F-droid. Works like a charm.

Do you mean a ground source heat pump? What is the lowest temperature there?

Not by much unfortunately. Car tires and brakes release very dangerous particles that are even smaller than PM2.5, but considering that the majority of cars are petrol cars, the pool of vehicles should be smaller.

It’s not really a big problem, there’s a very small minority of rich people. We can sort out the problem in less than a week.