I need to repaint some internal doors in my flat - the present coat is
a rather dull gloss, so it might be 'satin finish'.

Every paint tin 've read recommends that I sand down the paintwork
before repainting. The problem is, I have severe asthma, and I'm very
worried about the dust - both while I'm working, and afterwards when
I'm living in the room concerned. Even sanders that boast 'micro
filtration' only seem to guarantee to catch 80% of the dust.

I know this is a long-shot, but is there any alternative? A chemical
you can brush on, for instance?

Thanks in advance.