These are not strictly local but they are something that can be bought or made ‘once off’ and then available for local use for a long-time afterwards.

We have one high on our bedroom wall above the bed. It is important to remember to clean around it from time to time because it gets a big build-up of black particles that it has attracted out of the air we would otherwise breathe.

J. made ours with some readily-sourced electronic bits and pieces from an electronics shop and it works really well. Silent.