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The question What kinds of activities, experiment and, procedures done on the ISS must be done in chambers vented to space? links to and quotes from this answer to the 3D Printing SE question How is 3D printing done in space?

The issue there is particulates, and these are a problem for humans in all confined spaces and microgravity can pose extra risks both in clearing time and in the respiratory track (for the larger particles at least).

How are airborne particulates monitored on the ISS? Are they distinguished at all by size? Or type?

Are there real time monitors, and sampling systems where samples are sent to Earth for inspection?

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Sadly, they aren't really, except after the fact by looking at filters.

Particulate matter is removed from the air by HEPA filters located in the Common Cabin Air Assemblies (a fan/heat exchanger device). When my information was current, the filters were cleaned approximately every 90 days.

Some problems caused by accumulation of particles/dust are listed in the old paper ISS ECLSS Technology Evolution for Exploration

The unanticipated accumulation of a thick layer of lint on an intermodule ventilation fan's inlet screen led to degraded flow on-orbit. The buildup was due to passage of small lint through the subsystems inlet filter screens and subsequent aggregation into larger clumps which caused the flow blockage. As a result of the lack of fine particle settling in microgravity both the size distribution and quantity of particulate load differ substantially from that upon which the ventilation system's inlet screen was designed. To resolve the problem on ISS, a duct lint filter will be installed.

Ambient dust has caused the Node I smoke detector to trigger false positive alarms. Although the detector is located behind the cabin fan's inlet screen, dust is accumulating necessitating periodic cleaning by the crew. Characterization and accounting for background dust levels must be accounted for, or an alternate, dust- insensitive detector is needed.

The gasses making up the cabin atmosphere are monitored by a mass spectrometer called the Major Constituent Analyzer, but there is nothing to monitor particulate matter.

Sources: None public except the linked paper, because NASA doesn't care to publish technical details about the ISS in an organized way.

Addendum: User uhoh noted this experiment which at the time of writing had obtained one HEPA filter for post-flight analysis.

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  • $\begingroup$ A few months ago I'd seen something about a call for proposals or SBIR solicitation (I don't know the right adjectives) looking for designs that could effectively monitor particle counts and sizing on the ISS, but I can't find it now. It was certainly something that could apply to future stations as well. I'll keep looking. $\endgroup$ – uhoh Mar 3 '19 at 3:19
  • $\begingroup$ also, here's something you might consider quoting about off-line filter analysis: nasa.gov/mission_pages/station/research/experiments/900.html $\endgroup$ – uhoh Mar 3 '19 at 3:22
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    $\begingroup$ Thanks! Will take a look when not on my 'stone knives and bearskins' device. $\endgroup$ – Organic Marble Mar 3 '19 at 3:37
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    $\begingroup$ I ran across this while reading about PM2.5 on Earth. It's ten years old, but interesting: ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070031686.pdf $\endgroup$ – uhoh Mar 3 '19 at 9:30
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    $\begingroup$ As you wish. I'm kinda AFK for another week. $\endgroup$ – Organic Marble Mar 29 '19 at 13:39

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