Unless you stay in the one sealed room that the pure air is in then I can not see it helping much to be honest.
If you have a Dyson hover then turn that on in the room and see if it helps since it will be using the same kind of HEPA filters.
There's a thread in GC about it and the OP bought a Delonghi for a lot less money in the end and I think was very happy with it.
I see from the Dyson ads at the moment that it comes with a "free" spare filter that normally costs £50. I'll see if I can find it.