How do I keep sanding dust out of the rest of the house?

Almost all effort spent on dust goes into cleaning it up afterwards, which is the least effective point in the chain. The dust that matters is the fraction too fine to see, which stays airborne for hours and is drawn deep into the lungs. That fraction is captured at the tool or it is not captured at all.

Safety

What you'll need

• Workshop vacuum with the right hose adaptor
• Properly fitted respirator, FFP3 or a reusable half mask
• Plastic sheeting and low-tack tape
• Fan for the window (optional)
• Damp cloths and a microfibre mop
• Dust bag or pre-separator for the vacuum (optional)

Step by step

1. Extract at the tool first.Every random orbital sander, belt sander and most detail sanders have an extraction port. Connecting a workshop vacuum to it captures the majority of the dust before it enters the room. The onboard dust bag captures a small fraction of that. This one step matters more than everything else combined.
2. Make the adaptor work.Hose fittings rarely match between brands. A universal rubber stepped adaptor or a wrap of tape gets a decent seal, and a decent seal is what makes the extraction effective. It is worth ten minutes to get it right.
3. Check the disc holes line up with the pad.Extraction through a random orbital sander works through holes in the disc that must align with the holes in the pad. Misaligned discs cut extraction to almost nothing, and mesh or net discs avoid the problem entirely by extracting across the whole face.
4. Use a vacuum that will not blow the fine fraction straight back out.A general workshop vacuum without a fine filter passes the smallest particles through the motor and back into the room. Use a bagged machine, a HEPA-class filter, or a cyclone pre-separator ahead of it. This is the difference between removing dust and redistributing it.
5. Seal the room.Plastic sheeting taped across doorways, with a slit for access if you need to come and go. Tape over air bricks, extract vents, keyholes and the gaps around any internal doors. Lift or cover carpets and soft furnishings, because they hold fine dust for months.
6. Set up the airflow deliberately.A fan in the window blowing outwards puts the room under slight negative pressure, so air is drawn in under the door and dust goes out rather than into the rest of the house. A fan blowing inwards does exactly the opposite.
7. Wear a mask that actually fits.A disposable FFP3, or a reusable half mask with P3 filters, fitted so it seals against the face. Facial hair breaks the seal. A loose surgical-style or nuisance mask does nothing for fine wood dust.
8. Wet where you can, and never dry-sweep.Sweeping puts every settled particle back into the air. Vacuum with a fine filter, then wipe with damp cloths and a damp mop. Where the material allows it, wet sanding eliminates airborne dust entirely.
9. Give the air time before you unseal.Fine dust stays suspended for hours. Leave the extraction fan running for a good while after you stop work, and clean up before removing the sheeting rather than after.
10. Deal with clothes and equipment.Change outside the sealed area, wash work clothes separately, and vacuum the tools and the hose before carrying them through the house.

Tips

• Sanding outdoors solves most of this at a stroke. If a piece can be carried outside, carry it outside.
• MDF dust is the worst of the common materials for fineness and volume, and it deserves the full set of precautions rather than a token mask.
• Damp-wipe the walls and the tops of doors afterwards, not just the floor. Fine dust settles on every horizontal surface at every height.
• Keep an old duvet cover or sheet over anything upholstered that cannot be removed — fine dust in a sofa is a long-term problem.

If it doesn't work