Having long suffered with hayfever I finally purchased an air purifier and have had good results. The AirFree F40 is wall mounted and completely silent. Totally silent, zero decibels, no sound at all. It’s not “very quiet” there is literally no sound produced by the device at all!
It is designed to be permanently switched on and works by using a heating element and natural convection to make air flow through the device. The heated chamber allegedly reaches 200 Centigrade and incinerates any floating particles thus breaking them down into their constituent elements (Carbon, etc…).
I thought this might increase the amount of dust but have so far found no problems with it. The external device does get very warm to the touch but it is cool enough to keep my hand on it so should not cause any problems with the wall or any nearby furniture.
My night time symptoms seem to have been eased by using a purifier and I’m finding it easier to get to sleep now. I definitely recommend trying one if you have hayfever and can keep the room sealed except for entering/leaving.