The PSL room fans did not start up as usual this morning, which was noticeable in that after entering the PSL room, it was too quiet.  The fans were toggled on/off/on from the box inside the anti-room, without any change, and then toggled off/on from the box outside of the anti-room, and the fans started up, and ran without issue.

The PSL room fan situation led to a discussion about dust, and I mentioned that the IO optics are dusty, and I mentioned that when it's windy the dust counts in the PSL room increase.

Rick suggested the tubes that go through the PSL wall, near the floor under the light pipe, as a possible source for the dust, as part of the theory that during high winds, the LVEA is at a higher pressure that the PSL room, so dusty air is pushed into the PSL room.

I've looked at channels to see if I can identify situations that support LVEA air being injected into the PSL, and have found one 12 day period last year, where there are 3 events that raise the PSL level of dust,.  Two of the events are caused by wind, and one event is caused by entry into the PSL.

In the order of how much dust was measured in the PSL (highest to lowest):

event 1: 6/27/2017 ~1:19UTC - highlighted in red

• a gust of wind at 64 mph is measured at the Corner Station
• in the PSL, the 0.3 dust count from background (0-30 counts) to over 1000, and 0.5 counts go from background (0) to almost 200 counts
• the increase in dust in the PSL starts about 15 minutes later, and peaks at around 1040 counts (0.3) about 2 hours after the 64 mph gust
• it took about 10 hours for the PSL to return to background dust levels
• LVEA air only increases in 0.3 counts to around 440 counts
• this suggests that more dust was picked up as the LVEA air entered the PSL, OR the PSL itself was at that time, dusty enough to raise the 0.3 count above the LVEA count

event 2:  6/16/2017 ~8:50UTC - highlighted in orange

• wind increases from 10 mph to 35 mph, with some gusts, but none that rise above the overall increasing wind
• in the PSL, the 0.3 dust count from background (0-60 counts) to 350 counts, and 0.5 counts go from background (0) to almost 30 counts
• it took about 7 hours for the PSL to return to background dust levels

event 3: 6/20/2017 ~17:16UTC - highlighted in green

• people enter the PSL
• wind increases from 10 mph to 25 mph, with some gusts, but none that rise above the overall increasing wind
• in the PSL, the 0.3 dust count from background (0-60 counts) to 90 counts, and 0.5 counts go from background (0) to almost 30 counts
• it took about 5 hours for the PSL to return to background dust levels

These three events are shown in the two attached files:

• the first attachment shows two plots side by side,  focuses on PSL channels, and the three events are highlighted in red, orange, and green
• the second attachment shows one set of plots, focuses on PSL and LVEA channels, the LVEA dust channels are included, and only the fist channel is highlighted to identify the three events, all plots are on the same time scale
• three attachments that show each event zoomed in to a much shorter time span

- Rick, Cheryl