For the PSL HEPA, we wanted it to remain at full speed during the vent, when anyone is working on the PSL, or when there is a lot of dust due to outside conditions or cleaning in the lab.

For NORMAL conditions, the policy is to turn it to 30% for some flow, but low noise.

I think we ought to lock one of the arms on IR PDH and change the HEPA flow settings and plot the arm error signal, and transmitted power for each flow speed to see what's important. Record the times of each setting so that we can make a specgram later