table of contents and parent

###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](/wiki/air/particulatematter) and the direction dust comes from.

Passive monitoring promises to be less expensive and more robust than active monitors' mechanical and electrical components, but comes with a different set of challenges.  Public Lab is investigating one [promising passive monitor](???) as a tool for measuring airborne PM concentrations. 

###Advantages and Disadvantages

**Advantages** | **Disadvantages** 
--------------------|---------------------
low cost (less than $100 devices) | deployed for 3-7 days, low temporal resolution
deployed without electricity | not real-time (results must be analyzed after collection)
simple setup and calibration | analysis can be labor intensive or expensive
actual particles are collected | particle speciation is limited by method and cost
can generate airborne particle concentrations | no way to extrapolate to airborne concentrations of speciated particles
may correlate well with [Federal Reference Methods] | not an officially recognized method

###Devices

####SEM Stub Monitors
Developed originally for indoor dust monitoring at the University of North Carolina by Jeff Wagner and David Leith, this tiny monitor (in the middle of the housing, below) consists of a fine mesh cap over top of a Scanning Electron Microscopy (SEM) pin stub, a small aluminum object that looks like a pin.  Thomas Peters and Darrin Ott at the University of Iowa added a wind-and-rain housing so the monitors can be used outside.  They also added a glass microscope slide cover on top of the stub, allowing lower-cost analysis with a standard visible-light microscope. 

[![Amber Wise removing a stub cover](//i.publiclab.org/system/images/photos/000/012/171/original/IMG_20151020_175427.jpg)](//i.publiclab.org/system/images/photos/000/012/171/original/IMG_20151020_175427.jpg)

[![IMG_20151015_120027-trim.png](//i.publiclab.org/system/images/photos/000/013/521/medium/IMG_20151015_120027-trim.png)](//i.publiclab.org/system/images/photos/000/013/521/original/IMG_20151015_120027-trim.png)

This is the only passive particle monitor that is rated 

[Making a SEM stub monitor]
[Analyzing the results]