Did inspection of air ducting into the PSL enclosure. All appears to be in order. I found no breaks or damage to the ducting. The seals between the ducting and the hole in the roof were all intact. The damper on the discharge ducting is moving freely and appears to be working. 

   I did find pieces of insulation like material inside the discharge duct. This may be an artifact of the duct assembly. 

   Inspected the fan/filter units on top of the PSL Anti-room. All the prefilters are intact. They have expected surface contamination, but nothing out of the ordinary. In the "plenum" area between the prefilter and the fan unit (on the three fan/filter units inspected)I found moderate amounts of dust. The dust is concentrated around the edges of the plenum box, indicating it is outside the area of the air being drawn into the fan. At some point it may be good practice to clean these units, but this is not a pressing issue.

   Conclusion: Good News - The air ducting system seems to be operating as designed. It does not appear to be contributing to spikes in the particulate counts within the PSL Anti-room or laser enclosure. The HEPI filters were not inspected due to the disruption an inspection would cause.