Hi Fiona, as Lenora mentioned By by HEPA filtered air purifiers are very good . When I was in the BONS. I got them installed in every single room as the windows were closed due to construction. They have air intake adjustment 1-5. They could be a bit noisy at night so you could adjust it to 1or 2. We got them from IQair as I can remember. Hope this helps. They keep the room cool.
Thanks
Thressia