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###Introduction
A passive particle monitor measures particles without the use of mechanical or electrical systems, depending instead on natural wind-blown deposition of particles on a collection surface.  Passive particle monitoring is frequently used for qualitative "nuisance dust" measurements, and more recently to extrapolate airborne PM concentrations.  Passive monitoring promises to be less expensive and more robust than active monitors with mechanical and electrical components, but comes with a different set of challenges.  Public Lab has investigated one [promising passive monitor](???) as a tool for measuring airborne PM concentrations.