Don't know who is confusing who here. Not understanding this post - are we talking about particles or gases? You sanded something and measured particulates generated - well yes sanding generates particles. Machine sanding without extract makes those particles airborne. So manual plane and manual sand your timber, or use proper extract for machine use or a decent air fed mask. But if your concern is formaldehyde while you're processing timber then that seems to be a different case. Avoid processed panels, and avoid processes which heat or burn timber unless you have appropriate ventilation or an air fed mask.Just did some non extraction sanding of Oak and that meter went mental especially PM2.5 and PM10 ... The Formaldehyde increased only when the heat built up and burned!! Gasses?